<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:3b47d056-e317-474d-9e47-ff399938bc43,g:814b4c79-a0e1-462f-aae5-7d4aafabd488-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="smlp-20230930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_858a2aee-3887-4662-8f97-5af95666bd0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredUnitsIssued_d70a410c-d3b8-4477-9359-4bab1ef8bf0a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredUnitsIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_858a2aee-3887-4662-8f97-5af95666bd0f" xlink:to="loc_us-gaap_PreferredUnitsIssued_d70a410c-d3b8-4477-9359-4bab1ef8bf0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredUnitsOutstanding_b2b47d4c-c747-4120-b126-bbf4a67c1662" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_858a2aee-3887-4662-8f97-5af95666bd0f" xlink:to="loc_us-gaap_PreferredUnitsOutstanding_b2b47d4c-c747-4120-b126-bbf4a67c1662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAbstract_e1866c44-5391-4e55-8f33-b6756e4e6cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_858a2aee-3887-4662-8f97-5af95666bd0f" xlink:to="loc_us-gaap_PartnersCapitalAbstract_e1866c44-5391-4e55-8f33-b6756e4e6cf5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_8cc83f02-662b-4ae9-936d-bff6ec3b8fd5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnersCapitalAbstract_e1866c44-5391-4e55-8f33-b6756e4e6cf5" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsIssued_8cc83f02-662b-4ae9-936d-bff6ec3b8fd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_86e24962-efc7-41ed-b9c3-57a7ce1983bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnersCapitalAbstract_e1866c44-5391-4e55-8f33-b6756e4e6cf5" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_86e24962-efc7-41ed-b9c3-57a7ce1983bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c9eebc10-7f96-49fd-a15a-21bac19f18b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_858a2aee-3887-4662-8f97-5af95666bd0f" xlink:to="loc_us-gaap_StatementTable_c9eebc10-7f96-49fd-a15a-21bac19f18b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2a49a961-1586-499d-961c-0203e229beea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c9eebc10-7f96-49fd-a15a-21bac19f18b7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2a49a961-1586-499d-961c-0203e229beea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_2a49a961-1586-499d-961c-0203e229beea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2a49a961-1586-499d-961c-0203e229beea" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_2a49a961-1586-499d-961c-0203e229beea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_773083af-b54f-4035-a419-287576ad5da2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_2a49a961-1586-499d-961c-0203e229beea" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_773083af-b54f-4035-a419-287576ad5da2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SubsidiarySeriesAPreferredUnitsMember_b3c778f0-dda3-46e0-a061-a012ae7bec1e" xlink:href="smlp-20230930.xsd#smlp_SubsidiarySeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_773083af-b54f-4035-a419-287576ad5da2" xlink:to="loc_smlp_SubsidiarySeriesAPreferredUnitsMember_b3c778f0-dda3-46e0-a061-a012ae7bec1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_359d9c57-417f-4baa-9cdc-a03882ffc551" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_773083af-b54f-4035-a419-287576ad5da2" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_359d9c57-417f-4baa-9cdc-a03882ffc551" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="smlp-20230930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_da2ff6e3-6fc0-4e68-8521-0254f119739f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:to="loc_us-gaap_RevenuesAbstract_da2ff6e3-6fc0-4e68-8521-0254f119739f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_2fefaaf0-cb6c-40cf-8ce7-dc75753eb9a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_da2ff6e3-6fc0-4e68-8521-0254f119739f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_2fefaaf0-cb6c-40cf-8ce7-dc75753eb9a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_32b9e994-281d-4f9f-8da9-a00d9126fabf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_32b9e994-281d-4f9f-8da9-a00d9126fabf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_4d48db3d-9a77-43a2-a71c-de3e0e45d786" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_4d48db3d-9a77-43a2-a71c-de3e0e45d786" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_0012e44e-4e77-42cd-9ed2-e44ec647d7c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_0012e44e-4e77-42cd-9ed2-e44ec647d7c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_2cc6baf4-0813-4b44-8068-76db5305eefa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_2cc6baf4-0813-4b44-8068-76db5305eefa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_25826e99-80a8-4baf-8c24-dc751df4c2a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_25826e99-80a8-4baf-8c24-dc751df4c2a3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_da3b1063-d965-4ad9-9a59-01eae84a5499" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationIntegrationRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_da3b1063-d965-4ad9-9a59-01eae84a5499" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_2df2c19d-3210-4ff5-9a1b-a93bf7142f69" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_2df2c19d-3210-4ff5-9a1b-a93bf7142f69" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_e9eea6b5-7a6c-4d43-839e-0f019d468141" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_e9eea6b5-7a6c-4d43-839e-0f019d468141" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_8ef8d95f-0d8d-4e5e-9cbf-04a24062aa00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_CostsAndExpenses_8ef8d95f-0d8d-4e5e-9cbf-04a24062aa00" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseNet_a165875f-2f19-4ea2-81ba-725c0894836a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseNet_a165875f-2f19-4ea2-81ba-725c0894836a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_6f7223d7-8640-42ff-af8c-2461881b0b9f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_6f7223d7-8640-42ff-af8c-2461881b0b9f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfBusiness_c3d7cf9a-8d25-4e70-b404-f466d47ed5ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_GainLossOnSaleOfBusiness_c3d7cf9a-8d25-4e70-b404-f466d47ed5ee" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_a3eef28f-3feb-4bfe-8bd4-33458b5bd596" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_InterestExpense_a3eef28f-3feb-4bfe-8bd4-33458b5bd596" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_03eac415-3b4d-41eb-ba58-90587a5a11db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_03eac415-3b4d-41eb-ba58-90587a5a11db" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_726b7767-7e17-4f67-abb8-793ee05c68bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_726b7767-7e17-4f67-abb8-793ee05c68bd" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_757519fa-4e69-429f-a985-d70c80ec9067" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_757519fa-4e69-429f-a985-d70c80ec9067" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_83de5057-0a1a-4e6e-a4e4-a3e47472a8f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_ProfitLoss_83de5057-0a1a-4e6e-a4e4-a3e47472a8f5" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable_a38393ec-7fee-4f49-9665-9e52a888a9fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable_a38393ec-7fee-4f49-9665-9e52a888a9fe" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_fa3464f9-0094-46f8-b537-1a2d6661a124" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_NetIncomeLoss_fa3464f9-0094-46f8-b537-1a2d6661a124" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo_b398e52b-d0d7-428c-9a99-9f5de51a2aa6" xlink:href="smlp-20230930.xsd#smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo_b398e52b-d0d7-428c-9a99-9f5de51a2aa6" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_e40bed6e-9e95-43c4-a006-3ee938567b44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAllocatedToLimitedPartners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_216b175c-1fd5-48a9-aebc-c3a9f909919e" xlink:to="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_e40bed6e-9e95-43c4-a006-3ee938567b44" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerLimitedPartnershipUnitAbstract_00d2661b-4c9f-4f92-9c56-224a7b87fced" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerLimitedPartnershipUnitAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:to="loc_us-gaap_EarningsPerLimitedPartnershipUnitAbstract_00d2661b-4c9f-4f92-9c56-224a7b87fced" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax_add79ecd-17d3-48ea-9752-8d5dc3f7133a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerLimitedPartnershipUnitAbstract_00d2661b-4c9f-4f92-9c56-224a7b87fced" xlink:to="loc_us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax_add79ecd-17d3-48ea-9752-8d5dc3f7133a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted_6128586a-075c-4f49-8b6f-8c31636cf625" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerLimitedPartnershipUnitAbstract_00d2661b-4c9f-4f92-9c56-224a7b87fced" xlink:to="loc_us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted_6128586a-075c-4f49-8b6f-8c31636cf625" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_2c796543-ca52-47e1-b105-7c5f93de994f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_2c796543-ca52-47e1-b105-7c5f93de994f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding_e305699f-a0a1-4952-af04-e83507bcefe4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_2c796543-ca52-47e1-b105-7c5f93de994f" xlink:to="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding_e305699f-a0a1-4952-af04-e83507bcefe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted_67204292-03c0-4ddd-a78c-f0c9fdc79f51" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_2c796543-ca52-47e1-b105-7c5f93de994f" xlink:to="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted_67204292-03c0-4ddd-a78c-f0c9fdc79f51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_bc7a3f56-ca95-4fea-9463-bd27629df7b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c04bf3b9-a94b-4630-8539-f10b18ef7324" xlink:to="loc_us-gaap_StatementTable_bc7a3f56-ca95-4fea-9463-bd27629df7b2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_bd42b622-2d3f-4c99-a944-abb85f06e47c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bc7a3f56-ca95-4fea-9463-bd27629df7b2" xlink:to="loc_srt_ProductOrServiceAxis_bd42b622-2d3f-4c99-a944-abb85f06e47c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_bd42b622-2d3f-4c99-a944-abb85f06e47c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_bd42b622-2d3f-4c99-a944-abb85f06e47c" xlink:to="loc_srt_ProductsAndServicesDomain_bd42b622-2d3f-4c99-a944-abb85f06e47c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c6329a4c-aee5-45df-968b-ac603d9b4d2b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_bd42b622-2d3f-4c99-a944-abb85f06e47c" xlink:to="loc_srt_ProductsAndServicesDomain_c6329a4c-aee5-45df-968b-ac603d9b4d2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NaturalGasGatheringTransportationMarketingAndProcessingMember_6b7e742f-b480-45ff-9787-7236cbcf8ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NaturalGasGatheringTransportationMarketingAndProcessingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c6329a4c-aee5-45df-968b-ac603d9b4d2b" xlink:to="loc_us-gaap_NaturalGasGatheringTransportationMarketingAndProcessingMember_6b7e742f-b480-45ff-9787-7236cbcf8ba1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OilAndCondensateMember_91a4409d-a231-43f1-8a2c-82ea81ddb808" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OilAndCondensateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c6329a4c-aee5-45df-968b-ac603d9b4d2b" xlink:to="loc_us-gaap_OilAndCondensateMember_91a4409d-a231-43f1-8a2c-82ea81ddb808" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_102267f3-cbe7-4b6f-b368-3b51485a1c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c6329a4c-aee5-45df-968b-ac603d9b4d2b" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_102267f3-cbe7-4b6f-b368-3b51485a1c6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_a92c2c31-ffc3-4d08-83a3-db2499d93b37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bc7a3f56-ca95-4fea-9463-bd27629df7b2" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_a92c2c31-ffc3-4d08-83a3-db2499d93b37" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_a92c2c31-ffc3-4d08-83a3-db2499d93b37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_a92c2c31-ffc3-4d08-83a3-db2499d93b37" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_a92c2c31-ffc3-4d08-83a3-db2499d93b37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_542acea0-e228-4b4d-b981-91d3a5ddf54e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_a92c2c31-ffc3-4d08-83a3-db2499d93b37" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_542acea0-e228-4b4d-b981-91d3a5ddf54e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeriesAPreferredUnitsMember_8645f08e-2891-4c9d-8383-8be9bb5cf8d3" xlink:href="smlp-20230930.xsd#smlp_SeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_542acea0-e228-4b4d-b981-91d3a5ddf54e" xlink:to="loc_smlp_SeriesAPreferredUnitsMember_8645f08e-2891-4c9d-8383-8be9bb5cf8d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_CommonUnitsMember_6e7565d4-542b-4e5b-970e-2de21f6d681b" xlink:href="smlp-20230930.xsd#smlp_CommonUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_542acea0-e228-4b4d-b981-91d3a5ddf54e" xlink:to="loc_smlp_CommonUnitsMember_6e7565d4-542b-4e5b-970e-2de21f6d681b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_881654e8-cdad-4ad9-af7e-ad02f4d11501" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bc7a3f56-ca95-4fea-9463-bd27629df7b2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_881654e8-cdad-4ad9-af7e-ad02f4d11501" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_881654e8-cdad-4ad9-af7e-ad02f4d11501_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_881654e8-cdad-4ad9-af7e-ad02f4d11501" xlink:to="loc_srt_ConsolidatedEntitiesDomain_881654e8-cdad-4ad9-af7e-ad02f4d11501_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_6d7f878f-830f-4db5-a2b3-a0368d9be22c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_881654e8-cdad-4ad9-af7e-ad02f4d11501" xlink:to="loc_srt_ConsolidatedEntitiesDomain_6d7f878f-830f-4db5-a2b3-a0368d9be22c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_7192c97f-dba9-4037-802a-b0ae03efe18e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_6d7f878f-830f-4db5-a2b3-a0368d9be22c" xlink:to="loc_srt_SubsidiariesMember_7192c97f-dba9-4037-802a-b0ae03efe18e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFPARTNERSCAPITAL" xlink:type="simple" xlink:href="smlp-20230930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFPARTNERSCAPITAL"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFPARTNERSCAPITAL" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_fc1eecfe-0c4b-40a8-b264-c52dc8fea146" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_fc1eecfe-0c4b-40a8-b264-c52dc8fea146" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_fc7e9a51-f810-4043-a6dd-3f5b775e266d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_fc7e9a51-f810-4043-a6dd-3f5b775e266d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_ProfitLossExcludingSubsidiaryIncome_14764cea-6551-4450-8be2-67a1b1d85e53" xlink:href="smlp-20230930.xsd#smlp_ProfitLossExcludingSubsidiaryIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_smlp_ProfitLossExcludingSubsidiaryIncome_14764cea-6551-4450-8be2-67a1b1d85e53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitBasedCompensation_b30e1701-b10f-4986-be94-0ffefffa41fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountUnitBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitBasedCompensation_b30e1701-b10f-4986-be94-0ffefffa41fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalAccountTaxWithholdingForUnitBasedCompensation_0cf967d5-84ea-4d61-9c7c-1871a94959eb" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalAccountTaxWithholdingForUnitBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_smlp_PartnersCapitalAccountTaxWithholdingForUnitBasedCompensation_0cf967d5-84ea-4d61-9c7c-1871a94959eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalAccountIncreaseFromAssumptionOfNoncontrollingInterest_ef7b43d3-93b1-40f0-a67f-ae95bdcdd921" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalAccountIncreaseFromAssumptionOfNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_smlp_PartnersCapitalAccountIncreaseFromAssumptionOfNoncontrollingInterest_ef7b43d3-93b1-40f0-a67f-ae95bdcdd921" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountExchangesAndConversions_56e2e9df-16b8-4180-a294-614f8653c801" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountExchangesAndConversions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_50d873e9-ab1f-42ad-9ea2-dc22ddbb1547" xlink:to="loc_us-gaap_PartnersCapitalAccountExchangesAndConversions_56e2e9df-16b8-4180-a294-614f8653c801" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_b36b1ffb-519b-42f7-bf3a-46a759f6014f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_bfedf46b-6e3c-428d-ba35-698fc5947339" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_fc1eecfe-0c4b-40a8-b264-c52dc8fea146" xlink:to="loc_us-gaap_StatementTable_bfedf46b-6e3c-428d-ba35-698fc5947339" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4a5dff88-2a2c-4da2-9c68-562b8692b06c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bfedf46b-6e3c-428d-ba35-698fc5947339" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4a5dff88-2a2c-4da2-9c68-562b8692b06c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_4a5dff88-2a2c-4da2-9c68-562b8692b06c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4a5dff88-2a2c-4da2-9c68-562b8692b06c" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_4a5dff88-2a2c-4da2-9c68-562b8692b06c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_98ff1145-ae6c-4545-9732-3c82f796c4ea" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_4a5dff88-2a2c-4da2-9c68-562b8692b06c" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_98ff1145-ae6c-4545-9732-3c82f796c4ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalMember_af77fc50-1ce6-476d-a7d9-8993c7e18b28" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_98ff1145-ae6c-4545-9732-3c82f796c4ea" xlink:to="loc_smlp_PartnersCapitalMember_af77fc50-1ce6-476d-a7d9-8993c7e18b28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_31c16065-674e-43f6-b995-a387c1594f05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_bfedf46b-6e3c-428d-ba35-698fc5947339" xlink:to="loc_us-gaap_StatementClassOfStockAxis_31c16065-674e-43f6-b995-a387c1594f05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_31c16065-674e-43f6-b995-a387c1594f05_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_31c16065-674e-43f6-b995-a387c1594f05" xlink:to="loc_us-gaap_ClassOfStockDomain_31c16065-674e-43f6-b995-a387c1594f05_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_0dc02d30-fdfb-4315-95e4-176b0fc51ecc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_31c16065-674e-43f6-b995-a387c1594f05" xlink:to="loc_us-gaap_ClassOfStockDomain_0dc02d30-fdfb-4315-95e4-176b0fc51ecc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_61bae43f-3243-497b-b7c9-5525b9d39deb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_0dc02d30-fdfb-4315-95e4-176b0fc51ecc" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_61bae43f-3243-497b-b7c9-5525b9d39deb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="smlp-20230930.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_f929a811-d291-484f-9129-5cd1875442ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:to="loc_us-gaap_ProfitLoss_f929a811-d291-484f-9129-5cd1875442ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DepreciationDepletionAndAmortizationIncludingAmortizationOfAboveAndBelowMarketLeases_f63792b3-9ed3-4cd4-a1b9-108c6ae585ed" xlink:href="smlp-20230930.xsd#smlp_DepreciationDepletionAndAmortizationIncludingAmortizationOfAboveAndBelowMarketLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_smlp_DepreciationDepletionAndAmortizationIncludingAmortizationOfAboveAndBelowMarketLeases_f63792b3-9ed3-4cd4-a1b9-108c6ae585ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_ade959f9-e01f-4bb5-83b0-32af7d91de88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_ade959f9-e01f-4bb5-83b0-32af7d91de88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_f3cc9dfd-9dff-41df-8bb0-84ba4be4fe05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_f3cc9dfd-9dff-41df-8bb0-84ba4be4fe05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_734c3dd5-6f8f-4f23-ab8a-3953b4f0f897" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_ShareBasedCompensation_734c3dd5-6f8f-4f23-ab8a-3953b4f0f897" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_524582d7-1433-4705-bedc-ae6c7a18ae2d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_524582d7-1433-4705-bedc-ae6c7a18ae2d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_0348d862-ce0c-4fe3-851e-c6f1c9798e27" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentDividendsOrDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_0348d862-ce0c-4fe3-851e-c6f1c9798e27" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_GainLossOnSaleOfAssetsNet_b096b8e9-d6fe-4967-9deb-764354d4f23c" xlink:href="smlp-20230930.xsd#smlp_GainLossOnSaleOfAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_smlp_GainLossOnSaleOfAssetsNet_b096b8e9-d6fe-4967-9deb-764354d4f23c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_8b302f12-8885-489c-b15d-1670a6f00711" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_8b302f12-8885-489c-b15d-1670a6f00711" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOtherAssets_64fe6ef2-fde4-4124-8515-9f3a25a4a751" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_GainLossOnSaleOfOtherAssets_64fe6ef2-fde4-4124-8515-9f3a25a4a751" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_38afa603-abec-41dd-908b-828bb01056ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_38afa603-abec-41dd-908b-828bb01056ab" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_95c75c65-61c1-40ef-86af-c54bab194d30" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_95c75c65-61c1-40ef-86af-c54bab194d30" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_e1c3b07b-a57a-45eb-ac09-7bcb04791420" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_37694f71-d5b3-45d5-a701-44ae5d379259" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf_e1c3b07b-a57a-45eb-ac09-7bcb04791420" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_eb929819-1ebb-434a-bbfc-3abc34dda187" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_eb929819-1ebb-434a-bbfc-3abc34dda187" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableTrade_4451e021-0559-4327-8b80-523dbbb24a43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayableTrade"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableTrade_4451e021-0559-4327-8b80-523dbbb24a43" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_d3d1a439-a654-447e-8005-8437c2f509e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_d3d1a439-a654-447e-8005-8437c2f509e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_0ef6c825-a07e-4963-9b8b-f03e6dca3a99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_0ef6c825-a07e-4963-9b8b-f03e6dca3a99" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPropertyAndOtherTaxesPayable_6134d45d-618e-468e-9828-1a8bec46cd32" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPropertyAndOtherTaxesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInPropertyAndOtherTaxesPayable_6134d45d-618e-468e-9828-1a8bec46cd32" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_5d4b22ae-9583-4233-be11-895317b78796" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_5d4b22ae-9583-4233-be11-895317b78796" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInRegulatoryLiabilities_e914a87a-ee74-4ead-b92f-24d9fedbec06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInRegulatoryLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInRegulatoryLiabilities_e914a87a-ee74-4ead-b92f-24d9fedbec06" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_7c867d42-dbd4-4858-a3af-352b171feae2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_fd9114d8-e3d9-43a8-9cf0-9d5005eab005" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_7c867d42-dbd4-4858-a3af-352b171feae2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_e0bc1244-9c9e-4fd3-a49e-b3fcca36cb8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_e0c0f9c9-e425-487e-b7b0-96b4e9712b8e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_e0bc1244-9c9e-4fd3-a49e-b3fcca36cb8b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_60b010c4-678e-4579-bd60-9552382ae69f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_60b010c4-678e-4579-bd60-9552382ae69f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_7817d30a-f349-45d2-a7ec-d6e0da031408" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_7817d30a-f349-45d2-a7ec-d6e0da031408" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PaymentsForProceedsFromAssetSale_8b04495b-b871-484e-a97d-bc77399ac809" xlink:href="smlp-20230930.xsd#smlp_PaymentsForProceedsFromAssetSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_smlp_PaymentsForProceedsFromAssetSale_8b04495b-b871-484e-a97d-bc77399ac809" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_f870e4d6-0205-4729-94b1-2880d05b839c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_f870e4d6-0205-4729-94b1-2880d05b839c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_46c34865-ed55-45d5-a810-5744ae557f7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_46c34865-ed55-45d5-a810-5744ae557f7c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_c06a0615-966e-4f19-836b-a7b558d5a025" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_6d017469-7f6c-4425-a9e3-2bb8dab8d1f5" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_c06a0615-966e-4f19-836b-a7b558d5a025" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfSecuredDebt_24397d2f-8b8b-4685-aced-bf5dac587874" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_RepaymentsOfSecuredDebt_24397d2f-8b8b-4685-aced-bf5dac587874" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfSeniorDebt_20be0010-320b-454e-8dfa-da132b9a8972" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfSeniorDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_RepaymentsOfSeniorDebt_20be0010-320b-454e-8dfa-da132b9a8972" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_fca0e3b9-2a10-4705-a5bd-4d3a73945e42" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebt_fca0e3b9-2a10-4705-a5bd-4d3a73945e42" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfCapitalDistribution_49b97012-030f-4a31-b85d-d62395b4f36e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfCapitalDistribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_PaymentsOfCapitalDistribution_49b97012-030f-4a31-b85d-d62395b4f36e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfFinancingCosts_8d026508-2072-4034-8052-bd3a151f98c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_PaymentsOfFinancingCosts_8d026508-2072-4034-8052-bd3a151f98c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_50de9b17-eeb5-46b2-812b-0e200ef6fa55" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_50de9b17-eeb5-46b2-812b-0e200ef6fa55" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_8e4db28d-8f3a-4967-afc6-072981db5ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_4806e4f8-11bd-4448-976f-8c0a51bcc92d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_8e4db28d-8f3a-4967-afc6-072981db5ab7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_8314e8c4-d106-47dc-993d-bea8f1ed7d9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_8314e8c4-d106-47dc-993d-bea8f1ed7d9d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_b5dd6414-4099-49a1-9336-758e511ecd91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_b5dd6414-4099-49a1-9336-758e511ecd91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_fc231309-aaaa-4bf9-89f1-af852788b2f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f28e2b0f-b36a-4211-a3d1-e526372aec5b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_cdbc8299-e0da-435a-b58c-d8caebbaade5" xlink:to="loc_us-gaap_StatementTable_f28e2b0f-b36a-4211-a3d1-e526372aec5b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9e90de63-2b5a-448e-869e-8993d5d7fa12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f28e2b0f-b36a-4211-a3d1-e526372aec5b" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9e90de63-2b5a-448e-869e-8993d5d7fa12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9e90de63-2b5a-448e-869e-8993d5d7fa12_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9e90de63-2b5a-448e-869e-8993d5d7fa12" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_9e90de63-2b5a-448e-869e-8993d5d7fa12_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a8cdd6a4-b25a-4195-9286-ce4b8251aeac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_9e90de63-2b5a-448e-869e-8993d5d7fa12" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a8cdd6a4-b25a-4195-9286-ce4b8251aeac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LaneGPSystemMember_e6e6d329-ea58-4d8f-a63c-fd6243fca48e" xlink:href="smlp-20230930.xsd#smlp_LaneGPSystemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a8cdd6a4-b25a-4195-9286-ce4b8251aeac" xlink:to="loc_smlp_LaneGPSystemMember_e6e6d329-ea58-4d8f-a63c-fd6243fca48e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_BisonMidstreamLLCMember_4bd4b04b-c8ac-4f8b-a9c9-b662ba10c69b" xlink:href="smlp-20230930.xsd#smlp_BisonMidstreamLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a8cdd6a4-b25a-4195-9286-ce4b8251aeac" xlink:to="loc_smlp_BisonMidstreamLLCMember_4bd4b04b-c8ac-4f8b-a9c9-b662ba10c69b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/ACQUISTIONSANDDIVESTITURESNarrativeDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#ACQUISTIONSANDDIVESTITURESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/ACQUISTIONSANDDIVESTITURESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_223bfa23-6506-449e-99ae-abb998ed3c4a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_223bfa23-6506-449e-99ae-abb998ed3c4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown_e7a5f3b9-5ee3-482d-bc7e-2de547bdcc10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown_e7a5f3b9-5ee3-482d-bc7e-2de547bdcc10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_721b076c-815f-45ea-b632-5e87dbf0d70a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_721b076c-815f-45ea-b632-5e87dbf0d70a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsConsiderationOtherAdjustments_9ce89c19-945f-4655-8beb-90eb98da3163" xlink:href="smlp-20230930.xsd#smlp_DisposalGroupIncludingDiscontinuedOperationsConsiderationOtherAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsConsiderationOtherAdjustments_9ce89c19-945f-4655-8beb-90eb98da3163" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsNetBookValue_24db9cdd-4b57-43fd-b2f7-911ff1cc83ba" xlink:href="smlp-20230930.xsd#smlp_DisposalGroupIncludingDiscontinuedOperationsNetBookValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsNetBookValue_24db9cdd-4b57-43fd-b2f7-911ff1cc83ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsOtherCostsToSell_3e772a6f-9c2b-4a96-9d34-7bb4bc6e4ba4" xlink:href="smlp-20230930.xsd#smlp_DisposalGroupIncludingDiscontinuedOperationsOtherCostsToSell"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_smlp_DisposalGroupIncludingDiscontinuedOperationsOtherCostsToSell_3e772a6f-9c2b-4a96-9d34-7bb4bc6e4ba4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_aaf36fa0-1c38-464d-9ca7-9283728f4216" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f55ce372-bb26-41ec-a7f6-12efd914d99c" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_aaf36fa0-1c38-464d-9ca7-9283728f4216" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_089974d2-532d-4784-9b17-c8eb14d81002" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_aaf36fa0-1c38-464d-9ca7-9283728f4216" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_089974d2-532d-4784-9b17-c8eb14d81002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_089974d2-532d-4784-9b17-c8eb14d81002_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_089974d2-532d-4784-9b17-c8eb14d81002" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_089974d2-532d-4784-9b17-c8eb14d81002_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bdd34ba7-1870-4a7a-a224-21778ba5be92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_089974d2-532d-4784-9b17-c8eb14d81002" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bdd34ba7-1870-4a7a-a224-21778ba5be92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_OutriggerDJMember_c04cd886-1a83-4ebe-8a5b-20012bd4f13a" xlink:href="smlp-20230930.xsd#smlp_OutriggerDJMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bdd34ba7-1870-4a7a-a224-21778ba5be92" xlink:to="loc_smlp_OutriggerDJMember_c04cd886-1a83-4ebe-8a5b-20012bd4f13a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SterlingDJMember_267087c3-d197-490a-8a03-3b13e4d982a7" xlink:href="smlp-20230930.xsd#smlp_SterlingDJMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bdd34ba7-1870-4a7a-a224-21778ba5be92" xlink:to="loc_smlp_SterlingDJMember_267087c3-d197-490a-8a03-3b13e4d982a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_1b6010ff-d564-42f0-ad0e-c27ed227208f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_aaf36fa0-1c38-464d-9ca7-9283728f4216" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_1b6010ff-d564-42f0-ad0e-c27ed227208f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_1b6010ff-d564-42f0-ad0e-c27ed227208f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_1b6010ff-d564-42f0-ad0e-c27ed227208f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_1b6010ff-d564-42f0-ad0e-c27ed227208f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_ab660fd5-6d02-4a80-807d-33f149ccfbf4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_1b6010ff-d564-42f0-ad0e-c27ed227208f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_ab660fd5-6d02-4a80-807d-33f149ccfbf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_52601ecc-a833-485f-8ed6-9e0a0d890d79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_ab660fd5-6d02-4a80-807d-33f149ccfbf4" xlink:to="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_52601ecc-a833-485f-8ed6-9e0a0d890d79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4eac825c-2174-4991-b11a-deeb02d9cc86" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_aaf36fa0-1c38-464d-9ca7-9283728f4216" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4eac825c-2174-4991-b11a-deeb02d9cc86" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_4eac825c-2174-4991-b11a-deeb02d9cc86_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4eac825c-2174-4991-b11a-deeb02d9cc86" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_4eac825c-2174-4991-b11a-deeb02d9cc86_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_581d096f-9cd0-40ff-9def-ed861125e622" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_4eac825c-2174-4991-b11a-deeb02d9cc86" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_581d096f-9cd0-40ff-9def-ed861125e622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LaneGPSystemMember_537e39ba-e6e4-4bb3-9455-8128056abf46" xlink:href="smlp-20230930.xsd#smlp_LaneGPSystemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_581d096f-9cd0-40ff-9def-ed861125e622" xlink:to="loc_smlp_LaneGPSystemMember_537e39ba-e6e4-4bb3-9455-8128056abf46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_BisonMidstreamLLCMember_fb821123-e1df-49a1-87a6-046e1010a6d1" xlink:href="smlp-20230930.xsd#smlp_BisonMidstreamLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_581d096f-9cd0-40ff-9def-ed861125e622" xlink:to="loc_smlp_BisonMidstreamLLCMember_fb821123-e1df-49a1-87a6-046e1010a6d1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_d725c065-a858-4d1c-bd1b-de3cec836d88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_d725c065-a858-4d1c-bd1b-de3cec836d88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_2a50b868-bd8f-462c-9ad6-ee7a1974cab1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_2a50b868-bd8f-462c-9ad6-ee7a1974cab1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:to="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_11daa5a8-a385-4204-9143-26dc262f6c14_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:to="loc_srt_ProductsAndServicesDomain_11daa5a8-a385-4204-9143-26dc262f6c14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:to="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_GatheringServicesAndRelatedFeesMember_102274be-9a09-489d-b974-c6bfbe4a063b" xlink:href="smlp-20230930.xsd#smlp_GatheringServicesAndRelatedFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:to="loc_smlp_GatheringServicesAndRelatedFeesMember_102274be-9a09-489d-b974-c6bfbe4a063b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_5bc36cce-f3b5-4aa0-9e3d-a1cbdd4b8017" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_5bc36cce-f3b5-4aa0-9e3d-a1cbdd4b8017" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails_1" xlink:type="simple" xlink:href="smlp-20230930.xsd#REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails_1"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/REVENUEScheduleofEstimatedRevenueExpectedtobeRecognizedDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_d725c065-a858-4d1c-bd1b-de3cec836d88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_d725c065-a858-4d1c-bd1b-de3cec836d88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_2a50b868-bd8f-462c-9ad6-ee7a1974cab1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_2a50b868-bd8f-462c-9ad6-ee7a1974cab1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_f4eb371a-c83e-416f-8138-3087e535a712" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_77486a86-c38a-4006-8a7b-f6016d67457d" xlink:to="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_11daa5a8-a385-4204-9143-26dc262f6c14_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:to="loc_srt_ProductsAndServicesDomain_11daa5a8-a385-4204-9143-26dc262f6c14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_11daa5a8-a385-4204-9143-26dc262f6c14" xlink:to="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_GatheringServicesAndRelatedFeesMember_102274be-9a09-489d-b974-c6bfbe4a063b" xlink:href="smlp-20230930.xsd#smlp_GatheringServicesAndRelatedFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d98c2adc-8f84-4804-ae82-b04ef23f506f" xlink:to="loc_smlp_GatheringServicesAndRelatedFeesMember_102274be-9a09-489d-b974-c6bfbe4a063b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/REVENUEScheduleofDisaggregatedRevenuebyGeographicAreaandMajorProductsandServicesReportableSegmentsDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#REVENUEScheduleofDisaggregatedRevenuebyGeographicAreaandMajorProductsandServicesReportableSegmentsDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/REVENUEScheduleofDisaggregatedRevenuebyGeographicAreaandMajorProductsandServicesReportableSegmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_7b2c8a42-3358-46e1-8a04-e6c9b3bd9910" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_152bf0b7-0e98-4a93-8791-f2c7b41a1c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_7b2c8a42-3358-46e1-8a04-e6c9b3bd9910" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_152bf0b7-0e98-4a93-8791-f2c7b41a1c0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_a54b894b-bf90-43a3-9f1e-1f01575a4ca3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_7b2c8a42-3358-46e1-8a04-e6c9b3bd9910" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_a54b894b-bf90-43a3-9f1e-1f01575a4ca3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_afc1a777-049c-4e3f-b860-4bc0ed51b09a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a54b894b-bf90-43a3-9f1e-1f01575a4ca3" xlink:to="loc_srt_ProductOrServiceAxis_afc1a777-049c-4e3f-b860-4bc0ed51b09a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_afc1a777-049c-4e3f-b860-4bc0ed51b09a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_afc1a777-049c-4e3f-b860-4bc0ed51b09a" xlink:to="loc_srt_ProductsAndServicesDomain_afc1a777-049c-4e3f-b860-4bc0ed51b09a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1047fd99-cf24-4e34-bd32-5acb6d92d5b8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_afc1a777-049c-4e3f-b860-4bc0ed51b09a" xlink:to="loc_srt_ProductsAndServicesDomain_1047fd99-cf24-4e34-bd32-5acb6d92d5b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_GatheringServicesAndRelatedFeesMember_2d201d76-07aa-4b84-978f-0c0bf993114c" xlink:href="smlp-20230930.xsd#smlp_GatheringServicesAndRelatedFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1047fd99-cf24-4e34-bd32-5acb6d92d5b8" xlink:to="loc_smlp_GatheringServicesAndRelatedFeesMember_2d201d76-07aa-4b84-978f-0c0bf993114c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NaturalGasNGLAndCondensateSalesMember_324f5c0f-555d-4aa8-9970-a9fb9755c407" xlink:href="smlp-20230930.xsd#smlp_NaturalGasNGLAndCondensateSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1047fd99-cf24-4e34-bd32-5acb6d92d5b8" xlink:to="loc_smlp_NaturalGasNGLAndCondensateSalesMember_324f5c0f-555d-4aa8-9970-a9fb9755c407" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_c1179dc7-98cd-4cb6-a7ed-00b32e4d03f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1047fd99-cf24-4e34-bd32-5acb6d92d5b8" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_c1179dc7-98cd-4cb6-a7ed-00b32e4d03f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a54b894b-bf90-43a3-9f1e-1f01575a4ca3" xlink:to="loc_srt_ConsolidationItemsAxis_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1" xlink:to="loc_srt_ConsolidationItemsDomain_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_d0074d95-c28c-488e-844f-6cbe1fb092b9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_e7ab1bd4-8e68-4bd4-bc24-2944e88d67a1" xlink:to="loc_srt_ConsolidationItemsDomain_d0074d95-c28c-488e-844f-6cbe1fb092b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_f7261d77-81b1-4404-8a7b-e7db274dcb5f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_d0074d95-c28c-488e-844f-6cbe1fb092b9" xlink:to="loc_us-gaap_OperatingSegmentsMember_f7261d77-81b1-4404-8a7b-e7db274dcb5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_d2b81142-35a6-4b62-b59e-3fb580c39e15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_d0074d95-c28c-488e-844f-6cbe1fb092b9" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_d2b81142-35a6-4b62-b59e-3fb580c39e15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_ee38a2ee-3c43-40e9-a829-e01b857018fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_a54b894b-bf90-43a3-9f1e-1f01575a4ca3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_ee38a2ee-3c43-40e9-a829-e01b857018fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ee38a2ee-3c43-40e9-a829-e01b857018fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ee38a2ee-3c43-40e9-a829-e01b857018fe" xlink:to="loc_us-gaap_SegmentDomain_ee38a2ee-3c43-40e9-a829-e01b857018fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ee38a2ee-3c43-40e9-a829-e01b857018fe" xlink:to="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NortheastSegmentMember_64bba191-eed7-4330-946a-9dc389550327" xlink:href="smlp-20230930.xsd#smlp_NortheastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:to="loc_smlp_NortheastSegmentMember_64bba191-eed7-4330-946a-9dc389550327" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_RockiesSegmentMember_3975ccc8-c181-4d54-bdc4-8649beb64ba2" xlink:href="smlp-20230930.xsd#smlp_RockiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:to="loc_smlp_RockiesSegmentMember_3975ccc8-c181-4d54-bdc4-8649beb64ba2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianBasinSegmentMember_84995eff-bcfe-46e6-bd6e-47328427a874" xlink:href="smlp-20230930.xsd#smlp_PermianBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:to="loc_smlp_PermianBasinSegmentMember_84995eff-bcfe-46e6-bd6e-47328427a874" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PiceanceBasinSegmentMember_026055bd-8dfd-4140-a3fc-d3015e2e0ebd" xlink:href="smlp-20230930.xsd#smlp_PiceanceBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:to="loc_smlp_PiceanceBasinSegmentMember_026055bd-8dfd-4140-a3fc-d3015e2e0ebd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_BarnettShaleSegmentMember_6d0e7bd3-e35a-4948-bb14-dc7d496e92d5" xlink:href="smlp-20230930.xsd#smlp_BarnettShaleSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6052f68-2292-4593-9b08-7c5c68fb399d" xlink:to="loc_smlp_BarnettShaleSegmentMember_6d0e7bd3-e35a-4948-bb14-dc7d496e92d5" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/PROPERTYPLANTANDEQUIPMENTScheduleofPropertyPlantandEquipmentNetDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#PROPERTYPLANTANDEQUIPMENTScheduleofPropertyPlantandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/PROPERTYPLANTANDEQUIPMENTScheduleofPropertyPlantandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b04830fc-85be-488d-abd7-569ea1e5f4b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_51a8b53d-6b7f-4688-8c01-669075d0b331" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b04830fc-85be-488d-abd7-569ea1e5f4b6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_51a8b53d-6b7f-4688-8c01-669075d0b331" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_abd5e259-fdc2-4d8f-a810-4e041db4ba82" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b04830fc-85be-488d-abd7-569ea1e5f4b6" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_abd5e259-fdc2-4d8f-a810-4e041db4ba82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3030d4ee-97ce-4abd-9103-677b2273ae20" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b04830fc-85be-488d-abd7-569ea1e5f4b6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3030d4ee-97ce-4abd-9103-677b2273ae20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1caabde8-a251-4221-81de-768a5e4b167a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_b04830fc-85be-488d-abd7-569ea1e5f4b6" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1caabde8-a251-4221-81de-768a5e4b167a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4a09682b-ed0b-438b-a79f-d35cc8a487c3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1caabde8-a251-4221-81de-768a5e4b167a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4a09682b-ed0b-438b-a79f-d35cc8a487c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4a09682b-ed0b-438b-a79f-d35cc8a487c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4a09682b-ed0b-438b-a79f-d35cc8a487c3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_4a09682b-ed0b-438b-a79f-d35cc8a487c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4a09682b-ed0b-438b-a79f-d35cc8a487c3" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GasGatheringAndProcessingEquipmentMember_ab6c5c5e-3121-459a-81bf-13cada9d5f61" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GasGatheringAndProcessingEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:to="loc_us-gaap_GasGatheringAndProcessingEquipmentMember_ab6c5c5e-3121-459a-81bf-13cada9d5f61" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_31eb1fb2-3534-45ea-872a-9449586ce072" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:to="loc_us-gaap_ConstructionInProgressMember_31eb1fb2-3534-45ea-872a-9449586ce072" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LandandLineFillMember_49e21298-12bc-4ff8-9877-8e17f2d9f3fe" xlink:href="smlp-20230930.xsd#smlp_LandandLineFillMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:to="loc_smlp_LandandLineFillMember_49e21298-12bc-4ff8-9877-8e17f2d9f3fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember_9feeee79-c226-4334-8a1b-4a2ee06f1613" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_53177b71-8768-4f6d-b8e3-cb2c09f5d0cf" xlink:to="loc_us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember_9feeee79-c226-4334-8a1b-4a2ee06f1613" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/EQUITYMETHODINVESTMENTSScheduleofEquityMethodInvestmentsDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#EQUITYMETHODINVESTMENTSScheduleofEquityMethodInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/EQUITYMETHODINVESTMENTSScheduleofEquityMethodInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f9ee7b63-800d-4f7f-bb27-1b68716e96f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_6d130ff4-01a0-44a1-afed-4f5849fb34be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f9ee7b63-800d-4f7f-bb27-1b68716e96f2" xlink:to="loc_us-gaap_EquityMethodInvestments_6d130ff4-01a0-44a1-afed-4f5849fb34be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_407646fd-83cf-45d8-abb1-5b66392199c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_f9ee7b63-800d-4f7f-bb27-1b68716e96f2" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_407646fd-83cf-45d8-abb1-5b66392199c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6e36c0cc-3fa6-402a-958e-3d9ecda52836" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_407646fd-83cf-45d8-abb1-5b66392199c1" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6e36c0cc-3fa6-402a-958e-3d9ecda52836" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_6e36c0cc-3fa6-402a-958e-3d9ecda52836_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6e36c0cc-3fa6-402a-958e-3d9ecda52836" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_6e36c0cc-3fa6-402a-958e-3d9ecda52836_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_f19b8bf7-47e1-4dd4-8ab6-b324bf8d7d33" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6e36c0cc-3fa6-402a-958e-3d9ecda52836" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_f19b8bf7-47e1-4dd4-8ab6-b324bf8d7d33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DoubleECompanyLLCMember_602a7da1-77d8-43c5-8118-46392e947760" xlink:href="smlp-20230930.xsd#smlp_DoubleECompanyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_f19b8bf7-47e1-4dd4-8ab6-b324bf8d7d33" xlink:to="loc_smlp_DoubleECompanyLLCMember_602a7da1-77d8-43c5-8118-46392e947760" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_OhioGatheringCompanyLLCMember_852f4afd-b9ea-4c9c-a5b6-ca29763a04ee" xlink:href="smlp-20230930.xsd#smlp_OhioGatheringCompanyLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_f19b8bf7-47e1-4dd4-8ab6-b324bf8d7d33" xlink:to="loc_smlp_OhioGatheringCompanyLLCMember_852f4afd-b9ea-4c9c-a5b6-ca29763a04ee" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/DEBTComponentsofLongTermDebtDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#DEBTComponentsofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/DEBTComponentsofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_898d0355-dbc4-4ef6-8f4c-28ab703e7818" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_LineOfCredit_898d0355-dbc4-4ef6-8f4c-28ab703e7818" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_a949fc7e-e920-4de2-b905-528df1d2a941" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_a949fc7e-e920-4de2-b905-528df1d2a941" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredLongTermDebt_35e4a21f-1520-41fc-8960-36f2a0837b95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnsecuredLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_UnsecuredLongTermDebt_35e4a21f-1520-41fc-8960-36f2a0837b95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_5a24ac60-9601-416d-8e83-5e340d8ee304" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_5a24ac60-9601-416d-8e83-5e340d8ee304" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_6bea4d8d-c2c0-4b99-b464-f72f3505ab7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_LongTermDebt_6bea4d8d-c2c0-4b99-b464-f72f3505ab7c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_16a864d5-b964-4339-95bb-5ba6caaa0efb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_LongTermDebtCurrent_16a864d5-b964-4339-95bb-5ba6caaa0efb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_6f98bd0c-b21a-44ce-91fc-34b26480217d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_6f98bd0c-b21a-44ce-91fc-34b26480217d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a77d0a4a-e0da-48b6-b70f-eaf15a84ce5d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a77d0a4a-e0da-48b6-b70f-eaf15a84ce5d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_73e292f2-e771-4589-8231-608ad4aae5ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_589b2340-1c2d-4758-bccd-0fa2b193d4fa" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_73e292f2-e771-4589-8231-608ad4aae5ce" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1f4c1482-01a4-42fc-a015-6eac8ace0187" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_73e292f2-e771-4589-8231-608ad4aae5ce" xlink:to="loc_us-gaap_DebtInstrumentAxis_1f4c1482-01a4-42fc-a015-6eac8ace0187" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1f4c1482-01a4-42fc-a015-6eac8ace0187_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1f4c1482-01a4-42fc-a015-6eac8ace0187" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1f4c1482-01a4-42fc-a015-6eac8ace0187_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1f4c1482-01a4-42fc-a015-6eac8ace0187" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_AssetBackedLendingFacilityMember_ecfc7675-d131-4679-9052-cb09bdd92f60" xlink:href="smlp-20230930.xsd#smlp_AssetBackedLendingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:to="loc_smlp_AssetBackedLendingFacilityMember_ecfc7675-d131-4679-9052-cb09bdd92f60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianTransmissionTermLoanMember_c1d6035c-cdb8-4d9d-b445-92da0a820f68" xlink:href="smlp-20230930.xsd#smlp_PermianTransmissionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:to="loc_smlp_PermianTransmissionTermLoanMember_c1d6035c-cdb8-4d9d-b445-92da0a820f68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorNotesDueAprilTwentyTwentyFiveMember_9520e10a-8611-4a80-9964-0ff2df5b6880" xlink:href="smlp-20230930.xsd#smlp_SeniorNotesDueAprilTwentyTwentyFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:to="loc_smlp_SeniorNotesDueAprilTwentyTwentyFiveMember_9520e10a-8611-4a80-9964-0ff2df5b6880" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorSecuredNotesDue2026Member_32672e9b-db17-4c19-beaf-e341163ff3e5" xlink:href="smlp-20230930.xsd#smlp_SeniorSecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_924cfafe-84f5-4d50-8f06-21d79a515e7b" xlink:to="loc_smlp_SeniorSecuredNotesDue2026Member_32672e9b-db17-4c19-beaf-e341163ff3e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_8e100051-66b4-4d6b-88a2-ca74b49cae68" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_73e292f2-e771-4589-8231-608ad4aae5ce" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_8e100051-66b4-4d6b-88a2-ca74b49cae68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_8e100051-66b4-4d6b-88a2-ca74b49cae68_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_8e100051-66b4-4d6b-88a2-ca74b49cae68" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_8e100051-66b4-4d6b-88a2-ca74b49cae68_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_db7fff3d-2165-46db-9fe8-700a4c40d6cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_8e100051-66b4-4d6b-88a2-ca74b49cae68" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_db7fff3d-2165-46db-9fe8-700a4c40d6cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_fa8f7e2e-837f-40a5-8e0b-7a1ba86929e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_db7fff3d-2165-46db-9fe8-700a4c40d6cb" xlink:to="loc_us-gaap_LineOfCreditMember_fa8f7e2e-837f-40a5-8e0b-7a1ba86929e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_7fee6d81-492a-430d-ad03-e0e815e2fb38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_db7fff3d-2165-46db-9fe8-700a4c40d6cb" xlink:to="loc_us-gaap_SeniorNotesMember_7fee6d81-492a-430d-ad03-e0e815e2fb38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_7da42036-b18d-4722-bda1-e9dcf9490cf6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_db7fff3d-2165-46db-9fe8-700a4c40d6cb" xlink:to="loc_us-gaap_SecuredDebtMember_7da42036-b18d-4722-bda1-e9dcf9490cf6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/DEBTNarrativeDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#DEBTNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/DEBTNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_9f70aeda-074c-44d5-af5f-35d66210ff8e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_9f70aeda-074c-44d5-af5f-35d66210ff8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_aaed7786-3d9b-4487-9309-91b057109cbb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_aaed7786-3d9b-4487-9309-91b057109cbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantMandatoryRedemptionPeriod_8276cd0f-0ec5-4367-8c12-5ba0ff221ddc" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantMandatoryRedemptionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantMandatoryRedemptionPeriod_8276cd0f-0ec5-4367-8c12-5ba0ff221ddc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantMaximumAmountOutstandingForMaturity_d060d60c-9eef-43f7-b050-994aeedd2ab1" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantMaximumAmountOutstandingForMaturity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantMaximumAmountOutstandingForMaturity_d060d60c-9eef-43f7-b050-994aeedd2ab1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_e9ee5c90-3ecd-40f6-824d-e3d24c161d85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_e9ee5c90-3ecd-40f6-824d-e3d24c161d85" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_f8c487a7-61c1-4714-8907-19a06c2ad1bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_f8c487a7-61c1-4714-8907-19a06c2ad1bd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_4242f49f-f059-4dec-942b-cc8c2aae3c64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_4242f49f-f059-4dec-942b-cc8c2aae3c64" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_c0be3eae-70e4-4069-8d25-45ed73d7fe3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_LineOfCredit_c0be3eae-70e4-4069-8d25-45ed73d7fe3b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantFirstLienNetLeverageRatio_da1295d7-a4aa-44cd-8533-43a89d611487" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantFirstLienNetLeverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantFirstLienNetLeverageRatio_da1295d7-a4aa-44cd-8533-43a89d611487" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantInterestCoverageRatio_df0307e4-2944-45e2-b8cb-1397c452e747" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantInterestCoverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantInterestCoverageRatio_df0307e4-2944-45e2-b8cb-1397c452e747" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_c0ee0948-e955-4422-8722-afa608c228d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_c0ee0948-e955-4422-8722-afa608c228d6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_d368cfd8-9d0e-4507-9636-8b0a9871e66f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_d368cfd8-9d0e-4507-9636-8b0a9871e66f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_018e4c03-d38a-4349-98a8-a9e1c7e9df4f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_018e4c03-d38a-4349-98a8-a9e1c7e9df4f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DerivativeInstrumentPercentageOfDebtInstrument_b80e8689-31fe-4f89-ba1e-c1f0ed8604fa" xlink:href="smlp-20230930.xsd#smlp_DerivativeInstrumentPercentageOfDebtInstrument"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DerivativeInstrumentPercentageOfDebtInstrument_b80e8689-31fe-4f89-ba1e-c1f0ed8604fa" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_f368dde6-412e-4373-92ec-cd674deaed25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_f368dde6-412e-4373-92ec-cd674deaed25" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d63c35ec-2d79-4047-a49d-c47fedac6626" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_d63c35ec-2d79-4047-a49d-c47fedac6626" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentIssuedAsAPercentageOfFaceValue_3a5fe9b3-7fc4-4910-8dc3-43639bc8f87e" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentIssuedAsAPercentageOfFaceValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentIssuedAsAPercentageOfFaceValue_3a5fe9b3-7fc4-4910-8dc3-43639bc8f87e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_951070bf-dbab-4c4b-a529-35e979c59abe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_951070bf-dbab-4c4b-a529-35e979c59abe" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantRepurchaseAmountOfPrincipalPlusAccruedInterest_d029700f-6d1f-4c68-8221-ddf55f72b139" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantRepurchaseAmountOfPrincipalPlusAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantRepurchaseAmountOfPrincipalPlusAccruedInterest_d029700f-6d1f-4c68-8221-ddf55f72b139" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodOne_1609c4cf-f8ae-4ad2-bc5b-6d5837dea1f7" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodOne_1609c4cf-f8ae-4ad2-bc5b-6d5837dea1f7" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodOne_fdf0089e-2990-45bc-94e5-527dca1ec369" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodOne_fdf0089e-2990-45bc-94e5-527dca1ec369" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodTwo_0a6838ad-6544-41d1-8bc3-a705f2aec150" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodTwo_0a6838ad-6544-41d1-8bc3-a705f2aec150" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodTwo_00624e28-039c-4255-907f-53ef88b59a6a" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodTwo_00624e28-039c-4255-907f-53ef88b59a6a" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodThree_6978be6c-c041-4ef8-852b-a8d10a8d7cac" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchasePeriodThree_6978be6c-c041-4ef8-852b-a8d10a8d7cac" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodThree_a19392e6-9396-4c38-8280-ef3f34a840c1" xlink:href="smlp-20230930.xsd#smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_smlp_DebtInstrumentCovenantExcessCashFlowOfferToPurchaseBasisPointIncreasePeriodThree_a19392e6-9396-4c38-8280-ef3f34a840c1" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_3fbc0d1e-bc8a-4053-ae52-c9b2e4e3a59b" xlink:to="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9fad58a9-5833-40a3-928d-096809912eff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_us-gaap_DebtInstrumentAxis_9fad58a9-5833-40a3-928d-096809912eff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9fad58a9-5833-40a3-928d-096809912eff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9fad58a9-5833-40a3-928d-096809912eff" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9fad58a9-5833-40a3-928d-096809912eff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9fad58a9-5833-40a3-928d-096809912eff" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_ABLFacilityMember_c46edb1a-d52e-44bc-875c-0b9e29aaab44" xlink:href="smlp-20230930.xsd#smlp_ABLFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_ABLFacilityMember_c46edb1a-d52e-44bc-875c-0b9e29aaab44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_CreditAgreementMember_491a245a-ffa7-48f7-b60a-a7e3ae1b90ae" xlink:href="smlp-20230930.xsd#smlp_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_CreditAgreementMember_491a245a-ffa7-48f7-b60a-a7e3ae1b90ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianTransmissionTermLoanMember_08484cc8-e26b-42cc-b51a-ee05b54484f3" xlink:href="smlp-20230930.xsd#smlp_PermianTransmissionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_PermianTransmissionTermLoanMember_08484cc8-e26b-42cc-b51a-ee05b54484f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorSecuredSecondLienNotesDue2026Member_bbf23bd9-8a17-48f4-9ec6-c71c0c09ef88" xlink:href="smlp-20230930.xsd#smlp_SeniorSecuredSecondLienNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_SeniorSecuredSecondLienNotesDue2026Member_bbf23bd9-8a17-48f4-9ec6-c71c0c09ef88" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorSecuredNotesDue2026Member_3fceb120-a4ff-47b6-b408-c88884167a52" xlink:href="smlp-20230930.xsd#smlp_SeniorSecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_SeniorSecuredNotesDue2026Member_3fceb120-a4ff-47b6-b408-c88884167a52" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SecuredNotesIndenture2026Member_21743dfa-8a9b-4244-a7ed-4a0c2487530e" xlink:href="smlp-20230930.xsd#smlp_SecuredNotesIndenture2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_SecuredNotesIndenture2026Member_21743dfa-8a9b-4244-a7ed-4a0c2487530e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_TwoThousandTwentyFiveSeniorNotesMember_44f5c61c-1f4e-489a-a828-442be41eb078" xlink:href="smlp-20230930.xsd#smlp_TwoThousandTwentyFiveSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_3adbb229-753a-41e7-830a-4ff91660cde9" xlink:to="loc_smlp_TwoThousandTwentyFiveSeniorNotesMember_44f5c61c-1f4e-489a-a828-442be41eb078" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_3852446a-8f44-4893-a6f6-f1b47468f9e3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_us-gaap_CreditFacilityAxis_3852446a-8f44-4893-a6f6-f1b47468f9e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_3852446a-8f44-4893-a6f6-f1b47468f9e3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_3852446a-8f44-4893-a6f6-f1b47468f9e3" xlink:to="loc_us-gaap_CreditFacilityDomain_3852446a-8f44-4893-a6f6-f1b47468f9e3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_be09fe60-9400-4e08-b477-cf55b7322984" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_3852446a-8f44-4893-a6f6-f1b47468f9e3" xlink:to="loc_us-gaap_CreditFacilityDomain_be09fe60-9400-4e08-b477-cf55b7322984" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_dc395ac3-3b8b-4a08-af47-bf324c20a23e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_be09fe60-9400-4e08-b477-cf55b7322984" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_dc395ac3-3b8b-4a08-af47-bf324c20a23e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_TermLoanCreditFacilityMember_d9f762b6-83be-42f4-bb57-d696f310e6f1" xlink:href="smlp-20230930.xsd#smlp_TermLoanCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_be09fe60-9400-4e08-b477-cf55b7322984" xlink:to="loc_smlp_TermLoanCreditFacilityMember_d9f762b6-83be-42f4-bb57-d696f310e6f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_WorkingCapitalCreditFacilityMember_11a3929e-f823-4fb6-a5b2-e1bdbce4f061" xlink:href="smlp-20230930.xsd#smlp_WorkingCapitalCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_be09fe60-9400-4e08-b477-cf55b7322984" xlink:to="loc_smlp_WorkingCapitalCreditFacilityMember_11a3929e-f823-4fb6-a5b2-e1bdbce4f061" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_232488c4-b4c5-4a48-b1a7-cc9efcfd8527" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_us-gaap_VariableRateAxis_232488c4-b4c5-4a48-b1a7-cc9efcfd8527" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_232488c4-b4c5-4a48-b1a7-cc9efcfd8527_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_232488c4-b4c5-4a48-b1a7-cc9efcfd8527" xlink:to="loc_us-gaap_VariableRateDomain_232488c4-b4c5-4a48-b1a7-cc9efcfd8527_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_6338e96d-ba1f-4ca1-8d33-485a4b13016f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_232488c4-b4c5-4a48-b1a7-cc9efcfd8527" xlink:to="loc_us-gaap_VariableRateDomain_6338e96d-ba1f-4ca1-8d33-485a4b13016f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_1c82a29e-e2ac-456d-b49d-3390e9971032" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_6338e96d-ba1f-4ca1-8d33-485a4b13016f" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_1c82a29e-e2ac-456d-b49d-3390e9971032" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a361727e-2d59-4ed8-85b6-b32d2be02f04" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a361727e-2d59-4ed8-85b6-b32d2be02f04" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a361727e-2d59-4ed8-85b6-b32d2be02f04_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a361727e-2d59-4ed8-85b6-b32d2be02f04" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a361727e-2d59-4ed8-85b6-b32d2be02f04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_63b94306-8d71-47da-a859-fb42fcf0367a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a361727e-2d59-4ed8-85b6-b32d2be02f04" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_63b94306-8d71-47da-a859-fb42fcf0367a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_ad138500-8862-4dee-a8d0-a2230b09b798" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StandbyLettersOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_63b94306-8d71-47da-a859-fb42fcf0367a" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_ad138500-8862-4dee-a8d0-a2230b09b798" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_5b2831db-0a61-4d8d-8a75-ee297af4f7d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_5b2831db-0a61-4d8d-8a75-ee297af4f7d4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_5b2831db-0a61-4d8d-8a75-ee297af4f7d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_5b2831db-0a61-4d8d-8a75-ee297af4f7d4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_5b2831db-0a61-4d8d-8a75-ee297af4f7d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_db08f306-2084-494f-92fd-0bf2eb8193e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_5b2831db-0a61-4d8d-8a75-ee297af4f7d4" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_db08f306-2084-494f-92fd-0bf2eb8193e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_1cf62d39-9095-4deb-8cac-7ee77569cc4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_db08f306-2084-494f-92fd-0bf2eb8193e6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_1cf62d39-9095-4deb-8cac-7ee77569cc4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_b604eece-2740-4722-a193-d3409d876fa5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_db08f306-2084-494f-92fd-0bf2eb8193e6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_b604eece-2740-4722-a193-d3409d876fa5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_0d4f05c3-8bc3-4949-85f6-d212538cd6e5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_db08f306-2084-494f-92fd-0bf2eb8193e6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_0d4f05c3-8bc3-4949-85f6-d212538cd6e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_96911797-413e-43dd-a3cf-1511695932ea" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b3bc04ba-d542-492d-b489-4e7fed19b068" xlink:to="loc_dei_LegalEntityAxis_96911797-413e-43dd-a3cf-1511695932ea" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_96911797-413e-43dd-a3cf-1511695932ea_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_96911797-413e-43dd-a3cf-1511695932ea" xlink:to="loc_dei_EntityDomain_96911797-413e-43dd-a3cf-1511695932ea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_373e449e-28f8-4221-bc7b-aa6b9b7683b9" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_96911797-413e-43dd-a3cf-1511695932ea" xlink:to="loc_dei_EntityDomain_373e449e-28f8-4221-bc7b-aa6b9b7683b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SummitHoldingsAndFinanceCorporationMember_362774c5-c171-40b2-904a-e1173632f15e" xlink:href="smlp-20230930.xsd#smlp_SummitHoldingsAndFinanceCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_373e449e-28f8-4221-bc7b-aa6b9b7683b9" xlink:to="loc_smlp_SummitHoldingsAndFinanceCorporationMember_362774c5-c171-40b2-904a-e1173632f15e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SummitPermianTransmissionsLLCMember_b291fd1b-3aa5-4e56-9d30-a9639b9afce5" xlink:href="smlp-20230930.xsd#smlp_SummitPermianTransmissionsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_373e449e-28f8-4221-bc7b-aa6b9b7683b9" xlink:to="loc_smlp_SummitPermianTransmissionsLLCMember_b291fd1b-3aa5-4e56-9d30-a9639b9afce5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/DEBTScheduleofMaturitiesDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#DEBTScheduleofMaturitiesDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/DEBTScheduleofMaturitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_a3491e7f-8e94-4109-b9a5-5d7dbd1a6d8f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtByMaturityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_a3491e7f-8e94-4109-b9a5-5d7dbd1a6d8f" xlink:to="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_d277acc8-b485-43ae-89f8-99e59c8e514d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_d277acc8-b485-43ae-89f8-99e59c8e514d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_2960eaf8-9e75-4fb1-9cd9-f5b6d19f6414" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_2960eaf8-9e75-4fb1-9cd9-f5b6d19f6414" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_85d0aa00-0a74-455f-b8d3-5db805555f1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_85d0aa00-0a74-455f-b8d3-5db805555f1b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_fe7c0669-3d5c-4190-8961-35e0d675b48c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_fe7c0669-3d5c-4190-8961-35e0d675b48c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_2f86a9f1-d272-49f9-be29-eb6b40958834" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_2f86a9f1-d272-49f9-be29-eb6b40958834" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_4e3203ad-9edf-444c-a5a9-282e7e6206cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour_4e3203ad-9edf-444c-a5a9-282e7e6206cd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LongTermDebtMaturityAfterYearFour_79df119d-6e3a-4130-b1a5-c308d8a573c9" xlink:href="smlp-20230930.xsd#smlp_LongTermDebtMaturityAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_d418e5d6-c2c0-4aff-afac-cfd67eb58ca2" xlink:to="loc_smlp_LongTermDebtMaturityAfterYearFour_79df119d-6e3a-4130-b1a5-c308d8a573c9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_17a8c789-1091-426f-9768-99107277f556" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_a3491e7f-8e94-4109-b9a5-5d7dbd1a6d8f" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_17a8c789-1091-426f-9768-99107277f556" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_c174fd65-7fb8-43c1-a62c-20e3576bf6ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_17a8c789-1091-426f-9768-99107277f556" xlink:to="loc_us-gaap_DebtInstrumentAxis_c174fd65-7fb8-43c1-a62c-20e3576bf6ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c174fd65-7fb8-43c1-a62c-20e3576bf6ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_c174fd65-7fb8-43c1-a62c-20e3576bf6ef" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c174fd65-7fb8-43c1-a62c-20e3576bf6ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ee5e77d5-053b-4c19-aa3d-ff95524186b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_c174fd65-7fb8-43c1-a62c-20e3576bf6ef" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ee5e77d5-053b-4c19-aa3d-ff95524186b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianTransmissionTermLoanMember_5e4886e2-5730-46d3-8f29-dc1e8b847c85" xlink:href="smlp-20230930.xsd#smlp_PermianTransmissionTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee5e77d5-053b-4c19-aa3d-ff95524186b9" xlink:to="loc_smlp_PermianTransmissionTermLoanMember_5e4886e2-5730-46d3-8f29-dc1e8b847c85" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/FINANCIALINSTRUMENTSFairValueofDebtInstrumentsDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#FINANCIALINSTRUMENTSFairValueofDebtInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/FINANCIALINSTRUMENTSFairValueofDebtInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_ae3134db-9b9d-4b1f-b7d0-1540fb3295c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableFairValueDisclosure_c18c4180-53f8-4e3d-ac23-fdf827bdf4c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_ae3134db-9b9d-4b1f-b7d0-1540fb3295c0" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_c18c4180-53f8-4e3d-ac23-fdf827bdf4c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_ddb1be96-797b-4ba1-9679-9fd8446b95f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_ae3134db-9b9d-4b1f-b7d0-1540fb3295c0" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_ddb1be96-797b-4ba1-9679-9fd8446b95f6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_c452e4e7-694b-4285-8c34-9778c5cd38cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_ddb1be96-797b-4ba1-9679-9fd8446b95f6" xlink:to="loc_us-gaap_DebtInstrumentAxis_c452e4e7-694b-4285-8c34-9778c5cd38cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c452e4e7-694b-4285-8c34-9778c5cd38cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_c452e4e7-694b-4285-8c34-9778c5cd38cd" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c452e4e7-694b-4285-8c34-9778c5cd38cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_26de017b-903b-41ae-86c9-b88a302095a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_c452e4e7-694b-4285-8c34-9778c5cd38cd" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_26de017b-903b-41ae-86c9-b88a302095a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorNotesDue2025Member_8ba761f4-5558-4622-a880-c95011d69778" xlink:href="smlp-20230930.xsd#smlp_SeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_26de017b-903b-41ae-86c9-b88a302095a1" xlink:to="loc_smlp_SeniorNotesDue2025Member_8ba761f4-5558-4622-a880-c95011d69778" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeniorNotesDue2026Member_900d9dd1-23c8-449c-b009-8ed8f85a7f4b" xlink:href="smlp-20230930.xsd#smlp_SeniorNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_26de017b-903b-41ae-86c9-b88a302095a1" xlink:to="loc_smlp_SeniorNotesDue2026Member_900d9dd1-23c8-449c-b009-8ed8f85a7f4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_c177ddbb-022a-406a-b106-35476c58b700" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_ddb1be96-797b-4ba1-9679-9fd8446b95f6" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_c177ddbb-022a-406a-b106-35476c58b700" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c177ddbb-022a-406a-b106-35476c58b700_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_c177ddbb-022a-406a-b106-35476c58b700" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_c177ddbb-022a-406a-b106-35476c58b700_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_5263f0fb-220b-43f8-9aa7-3b6552647064" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_c177ddbb-022a-406a-b106-35476c58b700" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_5263f0fb-220b-43f8-9aa7-3b6552647064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_095238f5-a153-4227-8abf-31c9a25b988b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_5263f0fb-220b-43f8-9aa7-3b6552647064" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_095238f5-a153-4227-8abf-31c9a25b988b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_f325d6dd-6026-4aa8-bf91-7d659ff6f440" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_095238f5-a153-4227-8abf-31c9a25b988b" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_f325d6dd-6026-4aa8-bf91-7d659ff6f440" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_6c209f0c-66fa-4dc3-bd04-f9d91de4217e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_095238f5-a153-4227-8abf-31c9a25b988b" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_6c209f0c-66fa-4dc3-bd04-f9d91de4217e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_ddb1be96-797b-4ba1-9679-9fd8446b95f6" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_878d81c0-515e-4d68-bfdd-11c68568ad03" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_57ac42df-ec3d-4ad7-b0e2-6f9acd250fe4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_878d81c0-515e-4d68-bfdd-11c68568ad03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_73706b72-524c-4f69-bb7c-d1af0909782b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_878d81c0-515e-4d68-bfdd-11c68568ad03" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_73706b72-524c-4f69-bb7c-d1af0909782b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#FINANCIALINSTRUMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_ea7baf63-af7c-4436-bbbd-eefa47c686cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_ea7baf63-af7c-4436-bbbd-eefa47c686cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_66a4d6f5-fc42-4dda-a8c4-5bc9f0a76e64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_66a4d6f5-fc42-4dda-a8c4-5bc9f0a76e64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_770f98ba-8534-4e08-957f-68c7dc8f2e24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_770f98ba-8534-4e08-957f-68c7dc8f2e24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_fd9ee3e7-eaa2-4f7c-99c4-301e2b2f64bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_fd9ee3e7-eaa2-4f7c-99c4-301e2b2f64bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_3bb7cec0-a33d-496f-a623-f102a34cc6f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_f7d29eea-3e1f-44a3-97c4-5846e1c91c16" xlink:to="loc_us-gaap_ConcentrationRiskTable_3bb7cec0-a33d-496f-a623-f102a34cc6f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_3bb7cec0-a33d-496f-a623-f102a34cc6f4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b89bf6b6-2c4b-432e-87ca-7e3d0788795f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5560a5cd-8b1a-4ad4-9aaa-a0979c65c419" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b89bf6b6-2c4b-432e-87ca-7e3d0788795f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_b777980e-76f2-46e8-9a30-a8a183deedf6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_b89bf6b6-2c4b-432e-87ca-7e3d0788795f" xlink:to="loc_us-gaap_InterestRateSwapMember_b777980e-76f2-46e8-9a30-a8a183deedf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bd085987-3cd9-4be0-be3c-b4567c2953eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_3bb7cec0-a33d-496f-a623-f102a34cc6f4" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bd085987-3cd9-4be0-be3c-b4567c2953eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bd085987-3cd9-4be0-be3c-b4567c2953eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bd085987-3cd9-4be0-be3c-b4567c2953eb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_bd085987-3cd9-4be0-be3c-b4567c2953eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c1397118-23f5-4016-aae8-3fc32cecf764" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_bd085987-3cd9-4be0-be3c-b4567c2953eb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c1397118-23f5-4016-aae8-3fc32cecf764" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_c8319216-9a89-44c5-872c-f2a892bda604" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c1397118-23f5-4016-aae8-3fc32cecf764" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_c8319216-9a89-44c5-872c-f2a892bda604" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_62367763-235c-48dc-903a-b041c840de33" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_3bb7cec0-a33d-496f-a623-f102a34cc6f4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_62367763-235c-48dc-903a-b041c840de33" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_62367763-235c-48dc-903a-b041c840de33_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_62367763-235c-48dc-903a-b041c840de33" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_62367763-235c-48dc-903a-b041c840de33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03a1bec4-c18d-434e-96e9-3887b684fa0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_62367763-235c-48dc-903a-b041c840de33" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03a1bec4-c18d-434e-96e9-3887b684fa0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SterlingDJMember_3e7ee2cb-3861-4fed-b6da-b84265e8db5b" xlink:href="smlp-20230930.xsd#smlp_SterlingDJMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03a1bec4-c18d-434e-96e9-3887b684fa0f" xlink:to="loc_smlp_SterlingDJMember_3e7ee2cb-3861-4fed-b6da-b84265e8db5b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALPartnersCapitalandScheduleofUnitsDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#PARTNERSCAPITALANDMEZZANINECAPITALPartnersCapitalandScheduleofUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALPartnersCapitalandScheduleofUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_f64ea45c-acd7-4b9d-81a9-92726f503031" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_377da20e-ae12-4c74-a99d-e8f07387b445" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPartnersCapitalRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_f64ea45c-acd7-4b9d-81a9-92726f503031" xlink:to="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_377da20e-ae12-4c74-a99d-e8f07387b445" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnits_4577677f-56fa-4b32-ae0b-6e19230dbdad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_377da20e-ae12-4c74-a99d-e8f07387b445" xlink:to="loc_us-gaap_PartnersCapitalAccountUnits_4577677f-56fa-4b32-ae0b-6e19230dbdad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsUnitbasedCompensation_e6d67288-8422-4130-865d-777463a15053" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountUnitsUnitbasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_377da20e-ae12-4c74-a99d-e8f07387b445" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsUnitbasedCompensation_e6d67288-8422-4130-865d-777463a15053" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnits_1beb11e4-5f4c-4e25-8707-7dabf1fcca9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountUnits"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_008acd68-4664-4925-a99a-b9546844f5ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_f64ea45c-acd7-4b9d-81a9-92726f503031" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_008acd68-4664-4925-a99a-b9546844f5ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_7903b678-0875-4923-83a0-75fb5394bceb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_008acd68-4664-4925-a99a-b9546844f5ac" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_7903b678-0875-4923-83a0-75fb5394bceb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_7903b678-0875-4923-83a0-75fb5394bceb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_7903b678-0875-4923-83a0-75fb5394bceb" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_7903b678-0875-4923-83a0-75fb5394bceb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6dc1e345-e310-44a2-b11a-bde0b35a14b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_7903b678-0875-4923-83a0-75fb5394bceb" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6dc1e345-e310-44a2-b11a-bde0b35a14b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LimitedPartnerCommonUnitsMember_b46cb462-a7df-42d4-bf8c-ad96a112ba98" xlink:href="smlp-20230930.xsd#smlp_LimitedPartnerCommonUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6dc1e345-e310-44a2-b11a-bde0b35a14b7" xlink:to="loc_smlp_LimitedPartnerCommonUnitsMember_b46cb462-a7df-42d4-bf8c-ad96a112ba98" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALNarrativeDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#PARTNERSCAPITALANDMEZZANINECAPITALNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredUnitsOutstanding_f8e6f03f-e135-478c-9f03-dd0a0091b266" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_us-gaap_PreferredUnitsOutstanding_f8e6f03f-e135-478c-9f03-dd0a0091b266" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_AccruedAndUnpaidDistributions_188ff65a-322d-4efb-bcb2-618273ac7971" xlink:href="smlp-20230930.xsd#smlp_AccruedAndUnpaidDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_smlp_AccruedAndUnpaidDistributions_188ff65a-322d-4efb-bcb2-618273ac7971" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsConverted_c8e8a39d-924d-4fde-ad0e-f0a9d7379d24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapitalAccountUnitsConverted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsConverted_c8e8a39d-924d-4fde-ad0e-f0a9d7379d24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredUnitsIssued_6e1b88be-d2c6-4e99-a968-78952ce29582" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredUnitsIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_us-gaap_PreferredUnitsIssued_6e1b88be-d2c6-4e99-a968-78952ce29582" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_ContributedCapitalFromPreferredUnitsExchange_96ef66f0-9e06-422b-8ed0-5e4b6fe7a24c" xlink:href="smlp-20230930.xsd#smlp_ContributedCapitalFromPreferredUnitsExchange"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_smlp_ContributedCapitalFromPreferredUnitsExchange_96ef66f0-9e06-422b-8ed0-5e4b6fe7a24c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockRedemptionAmount_a59618fc-5db8-4d58-b46e-6f781ad608e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockRedemptionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_us-gaap_PreferredStockRedemptionAmount_a59618fc-5db8-4d58-b46e-6f781ad608e7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalIssuanceCosts_6e3a17a1-d5e5-4b80-8e2c-87cf26ded482" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_smlp_PartnersCapitalIssuanceCosts_6e3a17a1-d5e5-4b80-8e2c-87cf26ded482" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DistributionOfAllAvailableCashMaximumPeriodFollowingEndOfQuarter_307d100f-04f1-48ca-b39e-be0af2ea84d9" xlink:href="smlp-20230930.xsd#smlp_DistributionOfAllAvailableCashMaximumPeriodFollowingEndOfQuarter"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_smlp_DistributionOfAllAvailableCashMaximumPeriodFollowingEndOfQuarter_307d100f-04f1-48ca-b39e-be0af2ea84d9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalTable_4afad3d2-debf-4dc5-9a92-e63734850f13" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_smlp_PartnersCapitalLineItems_5cdf7651-05d4-47ec-a9cb-f4f11a4cfb1c" xlink:to="loc_smlp_PartnersCapitalTable_4afad3d2-debf-4dc5-9a92-e63734850f13" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_fcb92d2c-69f6-4e25-8bf2-75544d9798a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_smlp_PartnersCapitalTable_4afad3d2-debf-4dc5-9a92-e63734850f13" xlink:to="loc_us-gaap_StatementClassOfStockAxis_fcb92d2c-69f6-4e25-8bf2-75544d9798a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_fcb92d2c-69f6-4e25-8bf2-75544d9798a3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_fcb92d2c-69f6-4e25-8bf2-75544d9798a3" xlink:to="loc_us-gaap_ClassOfStockDomain_fcb92d2c-69f6-4e25-8bf2-75544d9798a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9d0298c7-a662-4275-8e44-6b5b0dbe4215" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_fcb92d2c-69f6-4e25-8bf2-75544d9798a3" xlink:to="loc_us-gaap_ClassOfStockDomain_9d0298c7-a662-4275-8e44-6b5b0dbe4215" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_a749c2b6-6126-42d2-a5a5-92203edc4571" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9d0298c7-a662-4275-8e44-6b5b0dbe4215" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_a749c2b6-6126-42d2-a5a5-92203edc4571" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0f7cde16-e07b-4218-be60-898f53d2f4d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_smlp_PartnersCapitalTable_4afad3d2-debf-4dc5-9a92-e63734850f13" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0f7cde16-e07b-4218-be60-898f53d2f4d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_0f7cde16-e07b-4218-be60-898f53d2f4d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0f7cde16-e07b-4218-be60-898f53d2f4d7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_0f7cde16-e07b-4218-be60-898f53d2f4d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_b8618f92-cf11-4837-aa05-c70f8f258bae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_0f7cde16-e07b-4218-be60-898f53d2f4d7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_b8618f92-cf11-4837-aa05-c70f8f258bae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_d6afd6ca-1ef0-4220-bf42-8061baae0645" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_b8618f92-cf11-4837-aa05-c70f8f258bae" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_d6afd6ca-1ef0-4220-bf42-8061baae0645" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SubsidiarySeriesAPreferredUnitsMember_2747023d-a20d-454f-a146-ecb4305572d0" xlink:href="smlp-20230930.xsd#smlp_SubsidiarySeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_b8618f92-cf11-4837-aa05-c70f8f258bae" xlink:to="loc_smlp_SubsidiarySeriesAPreferredUnitsMember_2747023d-a20d-454f-a146-ecb4305572d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_smlp_PartnersCapitalTable_4afad3d2-debf-4dc5-9a92-e63734850f13" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6f4253c6-5650-41b1-8c87-9f22af2c5aca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_8a77bc0c-f9a0-4c2d-98ef-4e920ad7a1ce" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6f4253c6-5650-41b1-8c87-9f22af2c5aca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LimitedPartnerCommonUnitsMember_c1300893-25e1-4feb-8706-74a59739d886" xlink:href="smlp-20230930.xsd#smlp_LimitedPartnerCommonUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_6f4253c6-5650-41b1-8c87-9f22af2c5aca" xlink:to="loc_smlp_LimitedPartnerCommonUnitsMember_c1300893-25e1-4feb-8706-74a59739d886" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALChangeinSubsidiaryDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#PARTNERSCAPITALANDMEZZANINECAPITALChangeinSubsidiaryDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/PARTNERSCAPITALANDMEZZANINECAPITALChangeinSubsidiaryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalLineItems_25b3fba2-ffa3-4bb9-84eb-957759485c12" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_97f05de9-aaeb-445f-9653-2539c50c1ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPartnersCapitalRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_25b3fba2-ffa3-4bb9-84eb-957759485c12" xlink:to="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_97f05de9-aaeb-445f-9653-2539c50c1ba1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_1f0fa8dd-3b79-4731-9a3c-dea75cbc4330" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_97f05de9-aaeb-445f-9653-2539c50c1ba1" xlink:to="loc_us-gaap_PartnersCapital_1f0fa8dd-3b79-4731-9a3c-dea75cbc4330" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_b4a4e5f6-ab77-4261-ab86-d920b0477707" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockAccretionOfRedemptionDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_97f05de9-aaeb-445f-9653-2539c50c1ba1" xlink:to="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_b4a4e5f6-ab77-4261-ab86-d920b0477707" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared_eafc9009-bc6d-4237-ba83-813d8d686937" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInPartnersCapitalRollForward_97f05de9-aaeb-445f-9653-2539c50c1ba1" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared_eafc9009-bc6d-4237-ba83-813d8d686937" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_7c130559-7126-4bb1-b51c-ee86b54cc79e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PartnersCapital"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionPayable_ced9dcab-a43e-4aed-95dd-4a52b6361a8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributionPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_smlp_PartnersCapitalLineItems_25b3fba2-ffa3-4bb9-84eb-957759485c12" xlink:to="loc_us-gaap_DistributionPayable_ced9dcab-a43e-4aed-95dd-4a52b6361a8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PartnersCapitalTable_da0bda5d-603a-4103-b9ac-393c353d9f27" xlink:href="smlp-20230930.xsd#smlp_PartnersCapitalTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_smlp_PartnersCapitalLineItems_25b3fba2-ffa3-4bb9-84eb-957759485c12" xlink:to="loc_smlp_PartnersCapitalTable_da0bda5d-603a-4103-b9ac-393c353d9f27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_de8a2798-93df-40d1-851e-9a69de6ab601" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_smlp_PartnersCapitalTable_da0bda5d-603a-4103-b9ac-393c353d9f27" xlink:to="loc_us-gaap_StatementClassOfStockAxis_de8a2798-93df-40d1-851e-9a69de6ab601" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_de8a2798-93df-40d1-851e-9a69de6ab601_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_de8a2798-93df-40d1-851e-9a69de6ab601" xlink:to="loc_us-gaap_ClassOfStockDomain_de8a2798-93df-40d1-851e-9a69de6ab601_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_a7f45e14-45f2-46e0-98a9-66a14da1458a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_de8a2798-93df-40d1-851e-9a69de6ab601" xlink:to="loc_us-gaap_ClassOfStockDomain_a7f45e14-45f2-46e0-98a9-66a14da1458a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_131edb95-98f3-4f04-ad91-ab536cb6acad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_a7f45e14-45f2-46e0-98a9-66a14da1458a" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_131edb95-98f3-4f04-ad91-ab536cb6acad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_91121fde-c402-45a7-b881-1ad78b213394" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_smlp_PartnersCapitalTable_da0bda5d-603a-4103-b9ac-393c353d9f27" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_91121fde-c402-45a7-b881-1ad78b213394" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_91121fde-c402-45a7-b881-1ad78b213394_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_91121fde-c402-45a7-b881-1ad78b213394" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_91121fde-c402-45a7-b881-1ad78b213394_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_ca57c02f-8090-4ad8-9d91-9e09517449ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_91121fde-c402-45a7-b881-1ad78b213394" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_ca57c02f-8090-4ad8-9d91-9e09517449ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeriesAPreferredUnitsMember_f534faee-2078-493b-b395-ec74a10b0360" xlink:href="smlp-20230930.xsd#smlp_SeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_ca57c02f-8090-4ad8-9d91-9e09517449ee" xlink:to="loc_smlp_SeriesAPreferredUnitsMember_f534faee-2078-493b-b395-ec74a10b0360" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/EARNINGSPERUNITDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#EARNINGSPERUNITDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/EARNINGSPERUNITDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_6430cbbd-bf64-4bf3-bcc9-8f5174848521" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_ProfitLoss_6430cbbd-bf64-4bf3-bcc9-8f5174848521" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable_3410a692-e7b0-4dd7-9a3f-5c306c84a099" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable_3410a692-e7b0-4dd7-9a3f-5c306c84a099" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_e3796392-2062-4cf1-9d70-e3bffce4486f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_NetIncomeLoss_e3796392-2062-4cf1-9d70-e3bffce4486f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo_05aff230-a4ed-4100-af8b-7f2794719826" xlink:href="smlp-20230930.xsd#smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_smlp_DeemedCapitalContributionFromPreferredExchangeOfferTwoThousandTwentyTwo_05aff230-a4ed-4100-af8b-7f2794719826" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_906bd1fa-3cd0-436b-8dda-24432fcca915" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAllocatedToLimitedPartners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_NetIncomeLossAllocatedToLimitedPartners_906bd1fa-3cd0-436b-8dda-24432fcca915" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding_fe969655-4d77-4a9c-a883-9268c002069c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding_fe969655-4d77-4a9c-a883-9268c002069c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_184529ac-3c11-4a2c-8b44-ec6ea9732b17" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_184529ac-3c11-4a2c-8b44-ec6ea9732b17" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted_6981aacc-1fe2-4628-afcf-67d1674546ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_WeightedAverageLimitedPartnershipUnitsOutstandingDiluted_6981aacc-1fe2-4628-afcf-67d1674546ab" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax_f6ed03f6-94c9-4cdb-88b4-98beb78a47ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax_f6ed03f6-94c9-4cdb-88b4-98beb78a47ad" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted_5390c366-a5fe-48d5-8450-b10ab469900c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted_5390c366-a5fe-48d5-8450-b10ab469900c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_614903fb-3bfd-4b51-9c25-636e8cc07fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_614903fb-3bfd-4b51-9c25-636e8cc07fe4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7507ab2c-10f8-4ca4-86bc-95aa18d45441" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_69d3b2d3-792b-45b4-a6cf-3f1f939d97b7" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7507ab2c-10f8-4ca4-86bc-95aa18d45441" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_c053f8f8-c997-4f09-9cd9-1834becf893f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7507ab2c-10f8-4ca4-86bc-95aa18d45441" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_c053f8f8-c997-4f09-9cd9-1834becf893f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_c053f8f8-c997-4f09-9cd9-1834becf893f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_c053f8f8-c997-4f09-9cd9-1834becf893f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_c053f8f8-c997-4f09-9cd9-1834becf893f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_118fd11f-d893-4a10-8a51-29055d63ae9c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_c053f8f8-c997-4f09-9cd9-1834becf893f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_118fd11f-d893-4a10-8a51-29055d63ae9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeriesAPreferredUnitsMember_087989fd-9e2c-4f6f-bc30-f7b551ca43fc" xlink:href="smlp-20230930.xsd#smlp_SeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_118fd11f-d893-4a10-8a51-29055d63ae9c" xlink:to="loc_smlp_SeriesAPreferredUnitsMember_087989fd-9e2c-4f6f-bc30-f7b551ca43fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_CommonUnitsMember_8d30b9b9-3f13-468b-aaa6-bb981521d202" xlink:href="smlp-20230930.xsd#smlp_CommonUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_118fd11f-d893-4a10-8a51-29055d63ae9c" xlink:to="loc_smlp_CommonUnitsMember_8d30b9b9-3f13-468b-aaa6-bb981521d202" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_c9378d81-0406-45ba-b17b-c677a6e4ea75" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7507ab2c-10f8-4ca4-86bc-95aa18d45441" xlink:to="loc_srt_ConsolidatedEntitiesAxis_c9378d81-0406-45ba-b17b-c677a6e4ea75" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_c9378d81-0406-45ba-b17b-c677a6e4ea75_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c9378d81-0406-45ba-b17b-c677a6e4ea75" xlink:to="loc_srt_ConsolidatedEntitiesDomain_c9378d81-0406-45ba-b17b-c677a6e4ea75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_e482cedd-81df-4022-a457-cd8302b78985" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_c9378d81-0406-45ba-b17b-c677a6e4ea75" xlink:to="loc_srt_ConsolidatedEntitiesDomain_e482cedd-81df-4022-a457-cd8302b78985" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_c9309c28-3b2e-43fb-9b56-d163af8fe8b9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e482cedd-81df-4022-a457-cd8302b78985" xlink:to="loc_srt_SubsidiariesMember_c9309c28-3b2e-43fb-9b56-d163af8fe8b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_d421e030-c97c-4922-abea-f9b63f23076d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_e482cedd-81df-4022-a457-cd8302b78985" xlink:to="loc_srt_ParentCompanyMember_d421e030-c97c-4922-abea-f9b63f23076d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/SUPPLEMENTALCASHFLOWINFORMATIONDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#SUPPLEMENTALCASHFLOWINFORMATIONDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/SUPPLEMENTALCASHFLOWINFORMATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_CondensedFinancialStatementsCaptionsLineItems_b330805e-a4c8-43dd-b42a-0ee85bb890e0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CondensedFinancialStatementsCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ec2b216-62cb-4a36-a6c7-538c7fa30aa5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CondensedFinancialStatementsCaptionsLineItems_b330805e-a4c8-43dd-b42a-0ee85bb890e0" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ec2b216-62cb-4a36-a6c7-538c7fa30aa5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_79222158-e4f6-49aa-b86c-16a115841f43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ec2b216-62cb-4a36-a6c7-538c7fa30aa5" xlink:to="loc_us-gaap_InterestPaidNet_79222158-e4f6-49aa-b86c-16a115841f43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaid_a0cbbd9d-452a-4e47-bf9f-fde14cceced0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ec2b216-62cb-4a36-a6c7-538c7fa30aa5" xlink:to="loc_us-gaap_IncomeTaxesPaid_a0cbbd9d-452a-4e47-bf9f-fde14cceced0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f24b5d85-7966-4d5a-b78e-13ef51c7a4af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CondensedFinancialStatementsCaptionsLineItems_b330805e-a4c8-43dd-b42a-0ee85bb890e0" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f24b5d85-7966-4d5a-b78e-13ef51c7a4af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_82396adb-a9e6-4d2d-be93-22dd0c47682d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f24b5d85-7966-4d5a-b78e-13ef51c7a4af" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_82396adb-a9e6-4d2d-be93-22dd0c47682d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_ea97cda6-f5eb-4e61-aee4-f189b8311ce4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockAccretionOfRedemptionDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f24b5d85-7966-4d5a-b78e-13ef51c7a4af" xlink:to="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_ea97cda6-f5eb-4e61-aee4-f189b8311ce4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromWarrantExercises_869b2266-7d0d-4ad7-9bf5-a529e14b597c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromWarrantExercises"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f24b5d85-7966-4d5a-b78e-13ef51c7a4af" xlink:to="loc_us-gaap_ProceedsFromWarrantExercises_869b2266-7d0d-4ad7-9bf5-a529e14b597c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfCondensedFinancialStatementsTable_e16758cb-682a-41d7-b063-26caf5747c13" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfCondensedFinancialStatementsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_CondensedFinancialStatementsCaptionsLineItems_b330805e-a4c8-43dd-b42a-0ee85bb890e0" xlink:to="loc_srt_ScheduleOfCondensedFinancialStatementsTable_e16758cb-682a-41d7-b063-26caf5747c13" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_ba8c7302-8656-4c7b-9284-e85a9783298c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ScheduleOfCondensedFinancialStatementsTable_e16758cb-682a-41d7-b063-26caf5747c13" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_ba8c7302-8656-4c7b-9284-e85a9783298c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_ba8c7302-8656-4c7b-9284-e85a9783298c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_ba8c7302-8656-4c7b-9284-e85a9783298c" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_ba8c7302-8656-4c7b-9284-e85a9783298c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_cb3dba57-fae1-43a2-b3b1-f2c8f60b763c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_ba8c7302-8656-4c7b-9284-e85a9783298c" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_cb3dba57-fae1-43a2-b3b1-f2c8f60b763c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_SeriesAPreferredUnitsMember_321cb624-6a35-4e6d-a30b-0bd74030d3b5" xlink:href="smlp-20230930.xsd#smlp_SeriesAPreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_cb3dba57-fae1-43a2-b3b1-f2c8f60b763c" xlink:to="loc_smlp_SeriesAPreferredUnitsMember_321cb624-6a35-4e6d-a30b-0bd74030d3b5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/UNITBASEDANDNONCASHCOMPENSATIONDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#UNITBASEDANDNONCASHCOMPENSATIONDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/UNITBASEDANDNONCASHCOMPENSATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_28a7c7ec-dc61-4d6e-9dc9-8d07fa56a370" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_28a7c7ec-dc61-4d6e-9dc9-8d07fa56a370" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a528560f-137b-4585-9c59-0744e4ff12e5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_a528560f-137b-4585-9c59-0744e4ff12e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_07721aef-7695-4434-9c55-6755e0474738" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_07721aef-7695-4434-9c55-6755e0474738" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_705d5cb8-8a11-40f9-87cf-6735fef04b69" xlink:href="smlp-20230930.xsd#smlp_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_smlp_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_705d5cb8-8a11-40f9-87cf-6735fef04b69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_449e9148-6aeb-4d93-9227-93ea4dde61ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_449e9148-6aeb-4d93-9227-93ea4dde61ce" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NumberOfDirectors_807316d2-ad1b-411a-8788-4d5e5834e0d8" xlink:href="smlp-20230930.xsd#smlp_NumberOfDirectors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_smlp_NumberOfDirectors_807316d2-ad1b-411a-8788-4d5e5834e0d8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue_30a20ff2-a796-42bb-a23a-6e41ecc7e76f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue_30a20ff2-a796-42bb-a23a-6e41ecc7e76f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_49bd95e7-d8ea-49b1-8845-441e5906cc18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_49bd95e7-d8ea-49b1-8845-441e5906cc18" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_00b700ce-f363-4f08-9ffd-cd1c268ed9af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_00b700ce-f363-4f08-9ffd-cd1c268ed9af" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d06c7f89-a2d5-4c9f-9631-4b5b33a586eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_efca3737-6233-436f-a242-eca62acfcaba" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d06c7f89-a2d5-4c9f-9631-4b5b33a586eb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d06c7f89-a2d5-4c9f-9631-4b5b33a586eb" xlink:to="loc_us-gaap_AwardTypeAxis_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ef27d94a-c41a-4331-a433-350d9a626083" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_84c3ad6a-6e18-43f3-8c90-b8a2bcf4d36f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ef27d94a-c41a-4331-a433-350d9a626083" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PhantomShareUnitsPSUsMember_38a01267-9fab-456c-ae45-0e7e33ed3010" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PhantomShareUnitsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ef27d94a-c41a-4331-a433-350d9a626083" xlink:to="loc_us-gaap_PhantomShareUnitsPSUsMember_38a01267-9fab-456c-ae45-0e7e33ed3010" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_c952165e-23d7-438c-9fe6-06e1e434c32c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ef27d94a-c41a-4331-a433-350d9a626083" xlink:to="loc_us-gaap_PerformanceSharesMember_c952165e-23d7-438c-9fe6-06e1e434c32c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_CommonUnitsMember_307460f2-2b69-4ad2-a354-a344ba46cc34" xlink:href="smlp-20230930.xsd#smlp_CommonUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ef27d94a-c41a-4331-a433-350d9a626083" xlink:to="loc_smlp_CommonUnitsMember_307460f2-2b69-4ad2-a354-a344ba46cc34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_3983754d-b2db-4455-b35c-9e836c96a657" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_d06c7f89-a2d5-4c9f-9631-4b5b33a586eb" xlink:to="loc_us-gaap_PlanNameAxis_3983754d-b2db-4455-b35c-9e836c96a657" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_3983754d-b2db-4455-b35c-9e836c96a657_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_3983754d-b2db-4455-b35c-9e836c96a657" xlink:to="loc_us-gaap_PlanNameDomain_3983754d-b2db-4455-b35c-9e836c96a657_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_de82a635-f1b2-46a2-a9f5-64359acd9a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_3983754d-b2db-4455-b35c-9e836c96a657" xlink:to="loc_us-gaap_PlanNameDomain_de82a635-f1b2-46a2-a9f5-64359acd9a5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_LongTermIncentivePlanMember_04001ea2-50d4-4200-8bae-c3033633bf44" xlink:href="smlp-20230930.xsd#smlp_LongTermIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_de82a635-f1b2-46a2-a9f5-64359acd9a5c" xlink:to="loc_smlp_LongTermIncentivePlanMember_04001ea2-50d4-4200-8bae-c3033633bf44" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/COMMITMENTSANDCONTINGENCIESScheduleofEnvironmentalMattersDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#COMMITMENTSANDCONTINGENCIESScheduleofEnvironmentalMattersDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/COMMITMENTSANDCONTINGENCIESScheduleofEnvironmentalMattersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_4b423973-2c2f-4107-b62a-f04a697216fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_c7997b3c-a4bc-4251-88d7-c1531d1b52ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4b423973-2c2f-4107-b62a-f04a697216fc" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_c7997b3c-a4bc-4251-88d7-c1531d1b52ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_40217e9e-5b22-4277-a048-5a8d518cf171" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_c7997b3c-a4bc-4251-88d7-c1531d1b52ad" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingencies_40217e9e-5b22-4277-a048-5a8d518cf171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPayments1_4a6659b9-2d1f-4074-be50-f71bc76b8412" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesPayments1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_c7997b3c-a4bc-4251-88d7-c1531d1b52ad" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPayments1_4a6659b9-2d1f-4074-be50-f71bc76b8412" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPeriodIncreaseDecrease_c983a129-3607-4f4c-b6fe-38cbf024f80f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccrualForEnvironmentalLossContingenciesRollForward_c7997b3c-a4bc-4251-88d7-c1531d1b52ad" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesPeriodIncreaseDecrease_c983a129-3607-4f4c-b6fe-38cbf024f80f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_502f1e13-846e-47f1-b746-b0be7b51c100" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_f81f0f5e-3b06-458f-9d78-b9a68552b0bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_4b423973-2c2f-4107-b62a-f04a697216fc" xlink:to="loc_us-gaap_LossContingenciesTable_f81f0f5e-3b06-458f-9d78-b9a68552b0bd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteAxis_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EnvironmentalRemediationSiteAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_f81f0f5e-3b06-458f-9d78-b9a68552b0bd" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteAxis_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteDomain_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EnvironmentalRemediationSiteDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteAxis_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteDomain_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationSiteDomain_fc568ce2-ca76-4810-97e5-2bcbbbd4e9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EnvironmentalRemediationSiteDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteAxis_b03f0b9f-5e70-4691-8852-c4eaa90a7e2e" xlink:to="loc_us-gaap_EnvironmentalRemediationSiteDomain_fc568ce2-ca76-4810-97e5-2bcbbbd4e9bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_MeadowlarkMidstreamGatheringSystemMember_6678c6b2-d297-43ab-91d0-7553b398bd59" xlink:href="smlp-20230930.xsd#smlp_MeadowlarkMidstreamGatheringSystemMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EnvironmentalRemediationSiteDomain_fc568ce2-ca76-4810-97e5-2bcbbbd4e9bc" xlink:to="loc_smlp_MeadowlarkMidstreamGatheringSystemMember_6678c6b2-d297-43ab-91d0-7553b398bd59" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#COMMITMENTSANDCONTINGENCIESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/COMMITMENTSANDCONTINGENCIESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_4137cd41-469b-4369-b337-95bc585ea09e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_4137cd41-469b-4369-b337-95bc585ea09e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses_d45e0728-6ef7-48f0-8b8b-a77f8fd8fbe0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses_d45e0728-6ef7-48f0-8b8b-a77f8fd8fbe0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_EnvironmentalLossContingenciesPenaltiesAndFinesPaymentPeriod_cb9cfc67-5c77-4009-85f4-7a09cac5ad7c" xlink:href="smlp-20230930.xsd#smlp_EnvironmentalLossContingenciesPenaltiesAndFinesPaymentPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_smlp_EnvironmentalLossContingenciesPenaltiesAndFinesPaymentPeriod_cb9cfc67-5c77-4009-85f4-7a09cac5ad7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate_dc4cca8b-e42c-4e2e-8ff5-b2d30978b308" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate_dc4cca8b-e42c-4e2e-8ff5-b2d30978b308" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_AccrualForEnvironmentalLossContingenciesExpectedPayment_7af27268-f52d-4263-8acd-c211074ebafb" xlink:href="smlp-20230930.xsd#smlp_AccrualForEnvironmentalLossContingenciesExpectedPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_smlp_AccrualForEnvironmentalLossContingenciesExpectedPayment_7af27268-f52d-4263-8acd-c211074ebafb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyClaimsSettledNumber_871dc648-be56-4d70-9de9-4ad2cd7eb821" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyClaimsSettledNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_LossContingencyClaimsSettledNumber_871dc648-be56-4d70-9de9-4ad2cd7eb821" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_d26d4c97-df4f-466d-a086-0673e7e944f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_d26d4c97-df4f-466d-a086-0673e7e944f8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_028c4672-a1ff-4b74-8f53-1f9cb6e33ffb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_4156cc4c-27a3-404b-b6c0-4ecc88aa750f" xlink:to="loc_us-gaap_LossContingenciesTable_028c4672-a1ff-4b74-8f53-1f9cb6e33ffb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_871de2ac-b957-48a9-a74d-31fb9a42243b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_028c4672-a1ff-4b74-8f53-1f9cb6e33ffb" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_871de2ac-b957-48a9-a74d-31fb9a42243b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_871de2ac-b957-48a9-a74d-31fb9a42243b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_871de2ac-b957-48a9-a74d-31fb9a42243b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_871de2ac-b957-48a9-a74d-31fb9a42243b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_871de2ac-b957-48a9-a74d-31fb9a42243b" xlink:to="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NaturalResourceDamagesToFederalAndStateGovernmentsMember_829e4b58-52f9-468b-ab92-2411fcf4a725" xlink:href="smlp-20230930.xsd#smlp_NaturalResourceDamagesToFederalAndStateGovernmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:to="loc_smlp_NaturalResourceDamagesToFederalAndStateGovernmentsMember_829e4b58-52f9-468b-ab92-2411fcf4a725" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DamagesPayableToFederalGovernmentOverFiveYearsMember_df7ffd8d-926d-4615-9c46-246a2da3836a" xlink:href="smlp-20230930.xsd#smlp_DamagesPayableToFederalGovernmentOverFiveYearsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:to="loc_smlp_DamagesPayableToFederalGovernmentOverFiveYearsMember_df7ffd8d-926d-4615-9c46-246a2da3836a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DamagesPayableToStateGovernmentsOverSixYearsMember_4d7a5797-37d1-485f-a6ab-b0516338734e" xlink:href="smlp-20230930.xsd#smlp_DamagesPayableToStateGovernmentsOverSixYearsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:to="loc_smlp_DamagesPayableToStateGovernmentsOverSixYearsMember_4d7a5797-37d1-485f-a6ab-b0516338734e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_DamagesPayableToFederalCriminalOverFiveYearsMember_934e5975-7046-45a6-ae74-1e1f246c3eb0" xlink:href="smlp-20230930.xsd#smlp_DamagesPayableToFederalCriminalOverFiveYearsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_dc959854-398e-4a36-a4b5-1e379f4fe5a3" xlink:to="loc_smlp_DamagesPayableToFederalCriminalOverFiveYearsMember_934e5975-7046-45a6-ae74-1e1f246c3eb0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_b59232f7-b574-41d7-8b6f-cf8874be590a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_028c4672-a1ff-4b74-8f53-1f9cb6e33ffb" xlink:to="loc_srt_LitigationCaseAxis_b59232f7-b574-41d7-8b6f-cf8874be590a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_b59232f7-b574-41d7-8b6f-cf8874be590a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_b59232f7-b574-41d7-8b6f-cf8874be590a" xlink:to="loc_srt_LitigationCaseTypeDomain_b59232f7-b574-41d7-8b6f-cf8874be590a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_0e8e21a2-405c-485f-930a-4af78b684ff0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_b59232f7-b574-41d7-8b6f-cf8874be590a" xlink:to="loc_srt_LitigationCaseTypeDomain_0e8e21a2-405c-485f-930a-4af78b684ff0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_A2015BlacktailReleaseMember_683f8b74-7f59-4c74-94b8-9bfe32a4ecac" xlink:href="smlp-20230930.xsd#smlp_A2015BlacktailReleaseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_0e8e21a2-405c-485f-930a-4af78b684ff0" xlink:to="loc_smlp_A2015BlacktailReleaseMember_683f8b74-7f59-4c74-94b8-9bfe32a4ecac" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/SEGMENTINFORMATIONAssetsRevenuesDepreciationandAmortizationandCapitalExpendituresbyReportableSegmentDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#SEGMENTINFORMATIONAssetsRevenuesDepreciationandAmortizationandCapitalExpendituresbyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/SEGMENTINFORMATIONAssetsRevenuesDepreciationandAmortizationandCapitalExpendituresbyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_ef6667f7-e8be-4960-b5ee-5bc9498280ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_a055ab47-92ae-4a56-8428-367cae7b0cec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_ef6667f7-e8be-4960-b5ee-5bc9498280ac" xlink:to="loc_us-gaap_Assets_a055ab47-92ae-4a56-8428-367cae7b0cec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0d76484c-c7f3-4fd3-8d61-b5ac4a89c341" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_ef6667f7-e8be-4960-b5ee-5bc9498280ac" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0d76484c-c7f3-4fd3-8d61-b5ac4a89c341" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_20ec3e60-42af-4ba6-9741-45e45918315a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0d76484c-c7f3-4fd3-8d61-b5ac4a89c341" xlink:to="loc_srt_ConsolidationItemsAxis_20ec3e60-42af-4ba6-9741-45e45918315a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_20ec3e60-42af-4ba6-9741-45e45918315a_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_20ec3e60-42af-4ba6-9741-45e45918315a" xlink:to="loc_srt_ConsolidationItemsDomain_20ec3e60-42af-4ba6-9741-45e45918315a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_69945172-ad8c-4332-a22e-ed23258e35a0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_20ec3e60-42af-4ba6-9741-45e45918315a" xlink:to="loc_srt_ConsolidationItemsDomain_69945172-ad8c-4332-a22e-ed23258e35a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_f387d4f1-1c5e-4503-bdde-4a294f3bdd24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_69945172-ad8c-4332-a22e-ed23258e35a0" xlink:to="loc_us-gaap_OperatingSegmentsMember_f387d4f1-1c5e-4503-bdde-4a294f3bdd24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_b898dc5f-b7df-4071-9231-a64fb1f74e3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_69945172-ad8c-4332-a22e-ed23258e35a0" xlink:to="loc_us-gaap_CorporateNonSegmentMember_b898dc5f-b7df-4071-9231-a64fb1f74e3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_1b82c80e-1d21-41a1-a196-7de45133074d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_0d76484c-c7f3-4fd3-8d61-b5ac4a89c341" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_1b82c80e-1d21-41a1-a196-7de45133074d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_1b82c80e-1d21-41a1-a196-7de45133074d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_1b82c80e-1d21-41a1-a196-7de45133074d" xlink:to="loc_us-gaap_SegmentDomain_1b82c80e-1d21-41a1-a196-7de45133074d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_1b82c80e-1d21-41a1-a196-7de45133074d" xlink:to="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_RockiesSegmentMember_9ff61720-999d-4066-95db-f08abdeb8aa9" xlink:href="smlp-20230930.xsd#smlp_RockiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:to="loc_smlp_RockiesSegmentMember_9ff61720-999d-4066-95db-f08abdeb8aa9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianBasinSegmentMember_fd7d1735-796b-467b-9437-074c6a8646f6" xlink:href="smlp-20230930.xsd#smlp_PermianBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:to="loc_smlp_PermianBasinSegmentMember_fd7d1735-796b-467b-9437-074c6a8646f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NortheastSegmentMember_3436bb94-2de4-44c8-acf8-3f61ff2ea56e" xlink:href="smlp-20230930.xsd#smlp_NortheastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:to="loc_smlp_NortheastSegmentMember_3436bb94-2de4-44c8-acf8-3f61ff2ea56e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PiceanceBasinSegmentMember_7161f891-8bfe-4587-84cb-77ca60206e60" xlink:href="smlp-20230930.xsd#smlp_PiceanceBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:to="loc_smlp_PiceanceBasinSegmentMember_7161f891-8bfe-4587-84cb-77ca60206e60" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_BarnettShaleSegmentMember_ce62afc8-9db6-43ca-ab1e-9e97f299a36a" xlink:href="smlp-20230930.xsd#smlp_BarnettShaleSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3900308-d657-45c9-b437-3015f846a10b" xlink:to="loc_smlp_BarnettShaleSegmentMember_ce62afc8-9db6-43ca-ab1e-9e97f299a36a" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.summitmidstream.com/role/SEGMENTINFORMATIONAdjustedEBITDAbyReportableSegmentDetails" xlink:type="simple" xlink:href="smlp-20230930.xsd#SEGMENTINFORMATIONAdjustedEBITDAbyReportableSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.summitmidstream.com/role/SEGMENTINFORMATIONAdjustedEBITDAbyReportableSegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_a5aa5ce1-9f38-4303-b37c-59cc655a9dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_a0de8c68-74ea-45ba-9965-cd6fcea907c1" xlink:href="smlp-20230930.xsd#smlp_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a5aa5ce1-9f38-4303-b37c-59cc655a9dd5" xlink:to="loc_smlp_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_a0de8c68-74ea-45ba-9965-cd6fcea907c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_90f81416-3391-4e07-a9f5-3ccf4270a097" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a5aa5ce1-9f38-4303-b37c-59cc655a9dd5" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_90f81416-3391-4e07-a9f5-3ccf4270a097" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_44872fe9-8277-44af-9919-b4a9ef74a539" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_90f81416-3391-4e07-a9f5-3ccf4270a097" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_44872fe9-8277-44af-9919-b4a9ef74a539" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_44872fe9-8277-44af-9919-b4a9ef74a539_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_44872fe9-8277-44af-9919-b4a9ef74a539" xlink:to="loc_us-gaap_SegmentDomain_44872fe9-8277-44af-9919-b4a9ef74a539_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_44872fe9-8277-44af-9919-b4a9ef74a539" xlink:to="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_RockiesSegmentMember_cc40e317-8fa8-4ac0-b7c8-c81e1c1ce9c1" xlink:href="smlp-20230930.xsd#smlp_RockiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:to="loc_smlp_RockiesSegmentMember_cc40e317-8fa8-4ac0-b7c8-c81e1c1ce9c1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PermianBasinSegmentMember_a2823461-830b-4c83-91dd-05b43f55bae0" xlink:href="smlp-20230930.xsd#smlp_PermianBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:to="loc_smlp_PermianBasinSegmentMember_a2823461-830b-4c83-91dd-05b43f55bae0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_NortheastSegmentMember_085c5b90-01e1-4ebb-8174-edc8579cce73" xlink:href="smlp-20230930.xsd#smlp_NortheastSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:to="loc_smlp_NortheastSegmentMember_085c5b90-01e1-4ebb-8174-edc8579cce73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_PiceanceBasinSegmentMember_3d4abac0-4e80-4f35-82e4-831010805625" xlink:href="smlp-20230930.xsd#smlp_PiceanceBasinSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:to="loc_smlp_PiceanceBasinSegmentMember_3d4abac0-4e80-4f35-82e4-831010805625" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_smlp_BarnettShaleSegmentMember_11586bed-87c8-44ff-aa2c-cce9c9457df2" xlink:href="smlp-20230930.xsd#smlp_BarnettShaleSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7343478a-8ff8-4dd4-8746-49b10888217b" xlink:to="loc_smlp_BarnettShaleSegmentMember_11586bed-87c8-44ff-aa2c-cce9c9457df2" xlink:type="arc" order="4"/>
  </link:definitionLink>
</link:linkbase>
