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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019fecad-89c4-7765-b867-31ed8d9bf3e8,g:41340087-0040-46d3-b98d-a5382ee0cdeb-->
<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://sm-energy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYUNAUDITEDinmillionsexceptsharedataanddividendspershare" xlink:type="simple" xlink:href="sm-20260930.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYUNAUDITEDinmillionsexceptsharedataanddividendspershare"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITYUNAUDITEDinmillionsexceptsharedataanddividendspershare" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019fecad-8bc0-77c9-bfa3-ed53097cfcef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019fecad-8bc0-71ad-b9c9-1c533e699c1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019fecad-8bc0-77c9-bfa3-ed53097cfcef" xlink:to="loc_us-gaap_StatementTable_019fecad-8bc0-71ad-b9c9-1c533e699c1a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019fecad-8bc0-7669-a5fd-fe2079290eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019fecad-8bc0-71ad-b9c9-1c533e699c1a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019fecad-8bc0-7669-a5fd-fe2079290eb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7669-a5fd-fe2079290eb6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019fecad-8bc0-7669-a5fd-fe2079290eb6" xlink:to="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7669-a5fd-fe2079290eb6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019fecad-8bc0-7669-a5fd-fe2079290eb6" xlink:to="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019fecad-8bc0-73f7-82c5-f37faa7a9d25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:to="loc_us-gaap_CommonStockMember_019fecad-8bc0-73f7-82c5-f37faa7a9d25" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019fecad-8bc0-7673-98b7-bb1b854377d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019fecad-8bc0-7673-98b7-bb1b854377d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019fecad-8bc0-7d1d-a5ab-55e5f1212a8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:to="loc_us-gaap_RetainedEarningsMember_019fecad-8bc0-7d1d-a5ab-55e5f1212a8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019fecad-8bc0-72be-a3c4-4f490db6bbff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019fecad-8bc0-7abf-bda4-275fdc4d9563" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019fecad-8bc0-72be-a3c4-4f490db6bbff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019fecad-8bc0-7323-bc19-8e48dd7c7cd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fecad-8bc0-77c9-bfa3-ed53097cfcef" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019fecad-8bc0-7323-bc19-8e48dd7c7cd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019fecad-8bc0-77c9-bfa3-ed53097cfcef" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019fecad-8bc0-70bb-8db1-4f79af1b149d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019fecad-8bc0-70bb-8db1-4f79af1b149d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019fecad-8bc0-7241-bb70-e2d2e276e3fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockholdersEquity_019fecad-8bc0-7241-bb70-e2d2e276e3fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019fecad-8bc0-7a71-8963-3276333ec224" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_NetIncomeLoss_019fecad-8bc0-7a71-8963-3276333ec224" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019fecad-8bc0-7e99-9521-d510a13b6741" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019fecad-8bc0-7e99-9521-d510a13b6741" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019fecad-8bc0-713e-9d3e-84a9de3292e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_DividendsCommonStockCash_019fecad-8bc0-713e-9d3e-84a9de3292e6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_019fecad-8bc0-7baf-b3d8-666d7ca66be5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_019fecad-8bc0-7baf-b3d8-666d7ca66be5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_019fecad-8bc0-7257-87e0-0b0665fce170" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_019fecad-8bc0-7257-87e0-0b0665fce170" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_StockIssuedDuringPeriodSharesRestrictedStockUnits_019fecad-8bc0-76ed-b3b9-f82cf195ec80" xlink:href="sm-20260930.xsd#sm_StockIssuedDuringPeriodSharesRestrictedStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_sm_StockIssuedDuringPeriodSharesRestrictedStockUnits_019fecad-8bc0-76ed-b3b9-f82cf195ec80" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_StockIssuedDuringPeriodValueRestrictedStockUnits_019fecad-8bc0-7115-94d2-e58708c56224" xlink:href="sm-20260930.xsd#sm_StockIssuedDuringPeriodValueRestrictedStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_sm_StockIssuedDuringPeriodValueRestrictedStockUnits_019fecad-8bc0-7115-94d2-e58708c56224" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019fecad-8bc0-7478-b1b6-862da8518b92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019fecad-8bc0-7478-b1b6-862da8518b92" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019fecad-8bc0-72fc-9668-8fb01374ec3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019fecad-8bc0-72fc-9668-8fb01374ec3f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019fecad-8bc0-77bd-bd95-f7bb417940d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019fecad-8bc0-77bd-bd95-f7bb417940d4" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_019fecad-8bc0-7404-bb0b-b2dbf6930b18" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_019fecad-8bc0-7404-bb0b-b2dbf6930b18" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_019fecad-8bc0-776f-81e9-2b7c1b39e8e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_019fecad-8bc0-776f-81e9-2b7c1b39e8e4" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019fecad-8bc0-7ab3-b559-8561ea59f48e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_019fecad-8bc0-7ab3-b559-8561ea59f48e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fecad-8bc0-7a8f-a570-9dac09647501" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019fecad-8bc0-741e-a3ce-1a9bea8f2711" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_019fecad-8bc0-7a8f-a570-9dac09647501" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019fecad-8bc0-7497-9ef2-032701614356" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019fecad-8bc0-767c-9d74-604d65fdbac1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/MergersAcquisitionsandDivestituresNarrativeDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#MergersAcquisitionsandDivestituresNarrativeDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/MergersAcquisitionsandDivestituresNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-737d-95c5-be8441347423" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-737d-95c5-be8441347423" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7618-b36b-80fa9b7a646b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-737d-95c5-be8441347423" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7618-b36b-80fa9b7a646b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7618-b36b-80fa9b7a646b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7618-b36b-80fa9b7a646b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7618-b36b-80fa9b7a646b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-72ba-ad76-841bd6439c7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7618-b36b-80fa9b7a646b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-72ba-ad76-841bd6439c7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-7270-98cc-536ccb173827" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-72ba-ad76-841bd6439c7e" xlink:to="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-7270-98cc-536ccb173827" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1_019fecad-8bc0-78f7-aa9a-21bb53d3921b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1_019fecad-8bc0-78f7-aa9a-21bb53d3921b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019fecad-8bc0-779d-b5aa-4cac538e8646" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_019fecad-8bc0-779d-b5aa-4cac538e8646" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableEntitySharesIssuedPerAcquireeShare_019fecad-8bc0-7738-be6b-0dea6b440b57" xlink:href="sm-20260930.xsd#sm_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableEntitySharesIssuedPerAcquireeShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_sm_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableEntitySharesIssuedPerAcquireeShare_019fecad-8bc0-7738-be6b-0dea6b440b57" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_019fecad-8bc0-73ca-b21e-f16bdd5c3114" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_019fecad-8bc0-73ca-b21e-f16bdd5c3114" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019fecad-8bc0-7ee1-b495-dd8359e934b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019fecad-8bc0-7ee1-b495-dd8359e934b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019fecad-8bc0-76d0-a067-b0c6a57eb431" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019fecad-8bc0-747e-97d8-e720d4455d9c" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019fecad-8bc0-76d0-a067-b0c6a57eb431" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:href="sm-20260930.xsd#sm_DisposalGroupLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DisposalGroupTable_019fecad-8bc0-74b8-bd97-20fe1f89502f" xlink:href="sm-20260930.xsd#sm_DisposalGroupTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:to="loc_sm_DisposalGroupTable_019fecad-8bc0-74b8-bd97-20fe1f89502f" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019fecad-8bc0-714a-a657-72efeb5cb4e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sm_DisposalGroupTable_019fecad-8bc0-74b8-bd97-20fe1f89502f" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019fecad-8bc0-714a-a657-72efeb5cb4e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019fecad-8bc0-714a-a657-72efeb5cb4e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019fecad-8bc0-714a-a657-72efeb5cb4e8" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019fecad-8bc0-714a-a657-72efeb5cb4e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019fecad-8bc0-720f-864e-0630cec7c096" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_019fecad-8bc0-714a-a657-72efeb5cb4e8" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019fecad-8bc0-720f-864e-0630cec7c096" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_SouthTexasDivestitureMember_019fecad-8bc0-74d9-88c4-950dedf590ee" xlink:href="sm-20260930.xsd#sm_SouthTexasDivestitureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_019fecad-8bc0-720f-864e-0630cec7c096" xlink:to="loc_sm_SouthTexasDivestitureMember_019fecad-8bc0-74d9-88c4-950dedf590ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sm_DisposalGroupTable_019fecad-8bc0-74b8-bd97-20fe1f89502f" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019fecad-8bc0-7ec0-a5cb-7f502abb523f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019fecad-8bc0-7e9d-a80b-d7c448ffd4b8" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019fecad-8bc0-7ec0-a5cb-7f502abb523f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_019fecad-8bc0-7a5d-a4d0-171c283bece9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019fecad-8bc0-7ec0-a5cb-7f502abb523f" xlink:to="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_019fecad-8bc0-7a5d-a4d0-171c283bece9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_01a19e04-1809-7e72-b82f-f49cbfb42379" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_sm_DisposalGroupTable_019fecad-8bc0-74b8-bd97-20fe1f89502f" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_01a19e04-1809-7e72-b82f-f49cbfb42379" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a19e04-1809-7e72-b82f-f49cbfb42379_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a19e04-1809-7e72-b82f-f49cbfb42379" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a19e04-1809-7e72-b82f-f49cbfb42379_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_01a19e04-1809-7edc-96ae-5e3ec7611579" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_01a19e04-1809-7e72-b82f-f49cbfb42379" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_01a19e04-1809-7edc-96ae-5e3ec7611579" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_01a19e04-3593-7edf-bc1f-a0035a3cd3fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_01a19e04-1809-7edc-96ae-5e3ec7611579" xlink:to="loc_us-gaap_SubsequentEventMember_01a19e04-3593-7edf-bc1f-a0035a3cd3fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DisposalGroupNotDiscontinuedOperationNetAcresDivested_019fecad-8bc0-7823-9b37-f93b3598b133" xlink:href="sm-20260930.xsd#sm_DisposalGroupNotDiscontinuedOperationNetAcresDivested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:to="loc_sm_DisposalGroupNotDiscontinuedOperationNetAcresDivested_019fecad-8bc0-7823-9b37-f93b3598b133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfOilAndGasPropertyAndEquipment_019fecad-8bc0-7c6e-9aee-c33f8af4c5a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfOilAndGasPropertyAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:to="loc_us-gaap_ProceedsFromSaleOfOilAndGasPropertyAndEquipment_019fecad-8bc0-7c6e-9aee-c33f8af4c5a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019fecad-8bc0-7988-adf9-b757c0ea5a24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnSaleOfOilAndGasProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:to="loc_us-gaap_GainLossOnSaleOfOilAndGasProperty_019fecad-8bc0-7988-adf9-b757c0ea5a24" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019fecad-8bc0-7823-8f12-06cf47b3c42f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DisposalGroupLineItems_019fecad-8bc0-7eb4-8403-01d4c729d498" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019fecad-8bc0-7823-8f12-06cf47b3c42f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/MergersAcquisitionsandDivestituresScheduleofPurchasePriceAllocationDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#MergersAcquisitionsandDivestituresScheduleofPurchasePriceAllocationDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/MergersAcquisitionsandDivestituresScheduleofPurchasePriceAllocationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-72ab-a71c-b00bb20cc482" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-72ab-a71c-b00bb20cc482" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-786e-82ee-d1242f6abf8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-72ab-a71c-b00bb20cc482" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-786e-82ee-d1242f6abf8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-786e-82ee-d1242f6abf8b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-786e-82ee-d1242f6abf8b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-786e-82ee-d1242f6abf8b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7972-b396-1d28f5ca0904" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-786e-82ee-d1242f6abf8b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7972-b396-1d28f5ca0904" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-78fa-a42b-47cfbfda0b93" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7972-b396-1d28f5ca0904" xlink:to="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-78fa-a42b-47cfbfda0b93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019fecad-8bc0-7f90-a2d3-7070eda75b95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019fecad-8bc0-7f90-a2d3-7070eda75b95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_019fecad-8bc0-7a1d-99df-2e33f0b6fe22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_019fecad-8bc0-7a1d-99df-2e33f0b6fe22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionSharePrice_019fecad-8bc0-7a2e-81a8-4245820b6474" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionSharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessAcquisitionSharePrice_019fecad-8bc0-7a2e-81a8-4245820b6474" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_019fecad-8bc0-7c31-a8bb-87ed93ec976b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_019fecad-8bc0-7c31-a8bb-87ed93ec976b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationConsiderationTransferredPreCombinationServicePortionOfReplacementEquityInterest_019fecad-8bc0-7adc-a2e2-0c8ae35f463e" xlink:href="sm-20260930.xsd#sm_BusinessCombinationConsiderationTransferredPreCombinationServicePortionOfReplacementEquityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_sm_BusinessCombinationConsiderationTransferredPreCombinationServicePortionOfReplacementEquityInterest_019fecad-8bc0-7adc-a2e2-0c8ae35f463e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019fecad-8bc0-7c4a-b656-d32b87e096af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019fecad-8bc0-7c4a-b656-d32b87e096af" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentProvedProperty_019fecad-8bc0-7893-9fcd-241e106ae7f8" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentProvedProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentProvedProperty_019fecad-8bc0-7893-9fcd-241e106ae7f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentUnprovedProperty_019fecad-8bc0-7be6-935a-1fba9a06d2dc" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentUnprovedProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_sm_BusinessCombinationRecognizedAssetAcquiredOilAndGasSuccessfulEffortsMethodPropertyAndEquipmentUnprovedProperty_019fecad-8bc0-7be6-935a-1fba9a06d2dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019fecad-8bc0-7ba2-a7a3-713514e81f1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019fecad-8bc0-7ba2-a7a3-713514e81f1f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedAssetAcquiredWellsInProgress_019fecad-8bc0-719e-b314-a1a1f9d64c62" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedAssetAcquiredWellsInProgress"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_sm_BusinessCombinationRecognizedAssetAcquiredWellsInProgress_019fecad-8bc0-719e-b314-a1a1f9d64c62" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019fecad-8bc0-77ba-b02d-aba3f94ac840" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther_019fecad-8bc0-77ba-b02d-aba3f94ac840" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019fecad-8bc0-79c9-a35d-394f15a800fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019fecad-8bc0-79c9-a35d-394f15a800fe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedAssetAcquiredDerivativeAsset_019fecad-8bc0-73f0-bae4-e6f2f3df90bb" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedAssetAcquiredDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_sm_BusinessCombinationRecognizedAssetAcquiredDerivativeAsset_019fecad-8bc0-73f0-bae4-e6f2f3df90bb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019fecad-8bc0-7c1c-86ad-483d89fa2d11" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019fecad-8bc0-7b55-91e9-1cb80aa6a8d8" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_019fecad-8bc0-7c1c-86ad-483d89fa2d11" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019fecad-8bc0-7087-9644-37ac5db383d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_019fecad-8bc0-7087-9644-37ac5db383d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019fecad-8bc0-7016-82a5-41c2ea3cacf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_019fecad-8bc0-7016-82a5-41c2ea3cacf9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_019fecad-8bc0-7a14-8b72-b0b11a6e2141" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities_019fecad-8bc0-7a14-8b72-b0b11a6e2141" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedLiabilityAssumedAssetRetirementObligation_019fecad-8bc0-7603-8610-915da24d1b37" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedLiabilityAssumedAssetRetirementObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_sm_BusinessCombinationRecognizedLiabilityAssumedAssetRetirementObligation_019fecad-8bc0-7603-8610-915da24d1b37" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_019fecad-8bc0-71af-832d-1b82973c75bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_019fecad-8bc0-71af-832d-1b82973c75bf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_BusinessCombinationRecognizedLiabilityAssumedDerivativeLiability_019fecad-8bc0-76c5-bf58-47d519144ef5" xlink:href="sm-20260930.xsd#sm_BusinessCombinationRecognizedLiabilityAssumedDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_sm_BusinessCombinationRecognizedLiabilityAssumedDerivativeLiability_019fecad-8bc0-76c5-bf58-47d519144ef5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_019fecad-8bc0-7162-96ca-acc6cb9e1d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_019fecad-8bc0-7162-96ca-acc6cb9e1d4e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019fecad-8bc0-7cff-b4de-34795457cbf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilitiesAbstract_019fecad-8bc0-73d8-8454-9156b9151567" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_019fecad-8bc0-7cff-b4de-34795457cbf4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019fecad-8bc0-72d7-948d-c1ae8fc458cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_019fecad-8bc0-72d7-948d-c1ae8fc458cc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_AssumedCreditFacilityDebtRepaid_019fecad-8bc0-761b-9f24-a119a3391561" xlink:href="sm-20260930.xsd#sm_AssumedCreditFacilityDebtRepaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_sm_AssumedCreditFacilityDebtRepaid_019fecad-8bc0-761b-9f24-a119a3391561" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_PaymentsToAcquireBusinessesGrossEmployeeRetentionProgram_019fecad-8bc0-70d5-aec8-6d7b4afe6ea2" xlink:href="sm-20260930.xsd#sm_PaymentsToAcquireBusinessesGrossEmployeeRetentionProgram"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7855-8991-2e453a0e59a0" xlink:to="loc_sm_PaymentsToAcquireBusinessesGrossEmployeeRetentionProgram_019fecad-8bc0-70d5-aec8-6d7b4afe6ea2" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/MergersAcquisitionsandDivestituresScheduleOfProFormaInformationDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#MergersAcquisitionsandDivestituresScheduleOfProFormaInformationDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/MergersAcquisitionsandDivestituresScheduleOfProFormaInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-7bc1-9f0b-2c370f0ac09a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-7bc1-9f0b-2c370f0ac09a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-783c-9248-52f4e782cfac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019fecad-8bc0-7bc1-9f0b-2c370f0ac09a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-783c-9248-52f4e782cfac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-783c-9248-52f4e782cfac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-783c-9248-52f4e782cfac" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-783c-9248-52f4e782cfac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7575-b77e-1db21e7d1966" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-783c-9248-52f4e782cfac" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7575-b77e-1db21e7d1966" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-7c02-b64a-747643657021" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7575-b77e-1db21e7d1966" xlink:to="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-7c02-b64a-747643657021" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_019fecad-8bc0-74af-8a2f-3096ed9d7f65" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_019fecad-8bc0-74af-8a2f-3096ed9d7f65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_019fecad-8bc0-7d23-8073-ecace98492d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_019fecad-8bc0-7d23-8073-ecace98492d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic_019fecad-8bc0-7ffd-9e64-eba2d6fdcf46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareBasic_019fecad-8bc0-7ffd-9e64-eba2d6fdcf46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted_019fecad-8bc0-76ad-be35-701ac2c8ac8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019fecad-8bc0-7416-922c-70ebf95307fe" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted_019fecad-8bc0-76ad-be35-701ac2c8ac8f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/DisaggregationofoilgasandNGLproductionrevenueDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#DisaggregationofoilgasandNGLproductionrevenueDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/DisaggregationofoilgasandNGLproductionrevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-782a-8283-9b45e547a401" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-782a-8283-9b45e547a401" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019fecad-8bc0-79b4-b431-f5c9927bca9d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:to="loc_srt_ProductOrServiceAxis_019fecad-8bc0-79b4-b431-f5c9927bca9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-79b4-b431-f5c9927bca9d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019fecad-8bc0-79b4-b431-f5c9927bca9d" xlink:to="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-79b4-b431-f5c9927bca9d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-70ff-9a2f-a15beaba1b78" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019fecad-8bc0-79b4-b431-f5c9927bca9d" xlink:to="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-70ff-9a2f-a15beaba1b78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CrudeOilMember_019fecad-8bc0-71a9-9c23-64290e90e02d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CrudeOilMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-70ff-9a2f-a15beaba1b78" xlink:to="loc_srt_CrudeOilMember_019fecad-8bc0-71a9-9c23-64290e90e02d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NaturalGasReservesMember_019fecad-8bc0-7968-aea3-64f11e420f2d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NaturalGasReservesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-70ff-9a2f-a15beaba1b78" xlink:to="loc_srt_NaturalGasReservesMember_019fecad-8bc0-7968-aea3-64f11e420f2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NaturalGasLiquidsReservesMember_019fecad-8bc0-75e9-a920-bc17b444e750" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NaturalGasLiquidsReservesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019fecad-8bc0-70ff-9a2f-a15beaba1b78" xlink:to="loc_srt_NaturalGasLiquidsReservesMember_019fecad-8bc0-75e9-a920-bc17b444e750" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fecad-8bc0-7a93-a3ab-a57e05b4706d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fecad-8bc0-7a93-a3ab-a57e05b4706d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fecad-8bc0-7a93-a3ab-a57e05b4706d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fecad-8bc0-7a93-a3ab-a57e05b4706d" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fecad-8bc0-7a93-a3ab-a57e05b4706d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fecad-8bc0-776d-8851-75996d0bf952" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019fecad-8bc0-7a93-a3ab-a57e05b4706d" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fecad-8bc0-776d-8851-75996d0bf952" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_019fecad-8bc0-7fd3-8afc-e2530ce4c8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019fecad-8bc0-776d-8851-75996d0bf952" xlink:to="loc_us-gaap_SalesRevenueNetMember_019fecad-8bc0-7fd3-8afc-e2530ce4c8f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019fecad-8bc0-7e80-9d24-cd3ddec543d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019fecad-8bc0-7e80-9d24-cd3ddec543d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019fecad-8bc0-7e80-9d24-cd3ddec543d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019fecad-8bc0-7e80-9d24-cd3ddec543d7" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019fecad-8bc0-7e80-9d24-cd3ddec543d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019fecad-8bc0-70f5-86d8-28d8cf60e7be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019fecad-8bc0-7e80-9d24-cd3ddec543d7" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019fecad-8bc0-70f5-86d8-28d8cf60e7be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_019fecad-8bc0-7288-9fa2-d935fb73a846" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019fecad-8bc0-70f5-86d8-28d8cf60e7be" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_019fecad-8bc0-7288-9fa2-d935fb73a846" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019fecad-8bc0-748a-9109-6e916831a430" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:to="loc_srt_StatementGeographicalAxis_019fecad-8bc0-748a-9109-6e916831a430" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-748a-9109-6e916831a430_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019fecad-8bc0-748a-9109-6e916831a430" xlink:to="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-748a-9109-6e916831a430_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019fecad-8bc0-748a-9109-6e916831a430" xlink:to="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_PermianBasinMember_019fecad-8bc0-766b-9d89-8cc78505cc27" xlink:href="sm-20260930.xsd#sm_PermianBasinMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:to="loc_sm_PermianBasinMember_019fecad-8bc0-766b-9d89-8cc78505cc27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DJBasinMember_019fecad-8bc0-72b8-80cc-1582ac764eb5" xlink:href="sm-20260930.xsd#sm_DJBasinMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:to="loc_sm_DJBasinMember_019fecad-8bc0-72b8-80cc-1582ac764eb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_SouthTexasMember_019fecad-8bc0-7c97-ab43-3df8c146e250" xlink:href="sm-20260930.xsd#sm_SouthTexasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:to="loc_sm_SouthTexasMember_019fecad-8bc0-7c97-ab43-3df8c146e250" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_UintaBasinMember_019fecad-8bc0-795d-b1d9-6ec73682bd37" xlink:href="sm-20260930.xsd#sm_UintaBasinMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019fecad-8bc0-7746-8795-df7921fd8007" xlink:to="loc_sm_UintaBasinMember_019fecad-8bc0-795d-b1d9-6ec73682bd37" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_01a1895d-6834-7e35-bc45-a416cc386f58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-70af-8e1b-465c23b67b6b" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_01a1895d-6834-7e35-bc45-a416cc386f58" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a1895d-6834-7e35-bc45-a416cc386f58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a1895d-6834-7e35-bc45-a416cc386f58" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a1895d-6834-7e35-bc45-a416cc386f58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a1895d-6834-792e-9dec-b30361402381" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_01a1895d-6834-7e35-bc45-a416cc386f58" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a1895d-6834-792e-9dec-b30361402381" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_01a1895d-6834-7ea3-8505-6fa8a82cf6e9" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_01a1895d-6834-792e-9dec-b30361402381" xlink:to="loc_sm_CivitasResourcesMergerMember_01a1895d-6834-7ea3-8505-6fa8a82cf6e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019fecad-8bc0-71f3-9624-f3c29ba7b427" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-782a-8283-9b45e547a401" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019fecad-8bc0-71f3-9624-f3c29ba7b427" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019fecad-8bc0-7848-85e3-b606180605ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-782a-8283-9b45e547a401" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019fecad-8bc0-7848-85e3-b606180605ff" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/AccountsReceivablefromCustomersDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#AccountsReceivablefromCustomersDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/AccountsReceivablefromCustomersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019fecad-8bc0-72a8-93ce-419effa3a42a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019fecad-8bc0-70a0-95c6-0621856c0525" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019fecad-8bc0-72a8-93ce-419effa3a42a" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019fecad-8bc0-70a0-95c6-0621856c0525" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019fecad-8bc0-7e68-9753-4386167cf167" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019fecad-8bc0-70a0-95c6-0621856c0525" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019fecad-8bc0-7e68-9753-4386167cf167" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_019fecad-8bc0-7e68-9753-4386167cf167_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019fecad-8bc0-7e68-9753-4386167cf167" xlink:to="loc_us-gaap_ReceivableTypeDomain_019fecad-8bc0-7e68-9753-4386167cf167_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_019fecad-8bc0-7575-8961-5a32baf7de24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019fecad-8bc0-7e68-9753-4386167cf167" xlink:to="loc_us-gaap_ReceivableTypeDomain_019fecad-8bc0-7575-8961-5a32baf7de24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeReceivableMember_019fecad-8bc0-7c23-9502-5b435b6df72d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedIncomeReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_019fecad-8bc0-7575-8961-5a32baf7de24" xlink:to="loc_us-gaap_AccruedIncomeReceivableMember_019fecad-8bc0-7c23-9502-5b435b6df72d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_019fecad-8bc0-701c-a1b2-9f407eba208a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019fecad-8bc0-72a8-93ce-419effa3a42a" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_019fecad-8bc0-701c-a1b2-9f407eba208a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/CreditAgreementDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#CreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/CreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_019fecad-8bc0-77dd-87a3-7c573f48751d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_019fecad-8bc0-77dd-87a3-7c573f48751d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019fecad-8bc0-7360-8023-6a0c2e9b2ac6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019fecad-8bc0-77dd-87a3-7c573f48751d" xlink:to="loc_us-gaap_CreditFacilityAxis_019fecad-8bc0-7360-8023-6a0c2e9b2ac6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019fecad-8bc0-7360-8023-6a0c2e9b2ac6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019fecad-8bc0-7360-8023-6a0c2e9b2ac6" xlink:to="loc_us-gaap_CreditFacilityDomain_019fecad-8bc0-7360-8023-6a0c2e9b2ac6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019fecad-8bc0-76b9-896b-dfa19053651c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019fecad-8bc0-7360-8023-6a0c2e9b2ac6" xlink:to="loc_us-gaap_CreditFacilityDomain_019fecad-8bc0-76b9-896b-dfa19053651c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019fecad-8bc0-7236-9d00-bb650942866e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019fecad-8bc0-76b9-896b-dfa19053651c" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019fecad-8bc0-7236-9d00-bb650942866e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7927-a7d1-3e611db221ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019fecad-8bc0-77dd-87a3-7c573f48751d" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7927-a7d1-3e611db221ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7927-a7d1-3e611db221ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7927-a7d1-3e611db221ee" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7927-a7d1-3e611db221ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7d1d-b36d-8d0001198c90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7927-a7d1-3e611db221ee" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7d1d-b36d-8d0001198c90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7fdf-bd04-4a2b2abce4ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7d1d-b36d-8d0001198c90" xlink:to="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7fdf-bd04-4a2b2abce4ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019fecad-8bc0-750b-849a-00fcccc9207d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019fecad-8bc0-750b-849a-00fcccc9207d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019fecad-8bc0-7fe7-a56b-5ae889190f03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_019fecad-8bc0-7fe7-a56b-5ae889190f03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_LineOfCreditFacilityAggregateRevolvingLenderCommitments_019fecad-8bc0-70b4-8b3e-f5d9817a1f98" xlink:href="sm-20260930.xsd#sm_LineOfCreditFacilityAggregateRevolvingLenderCommitments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_sm_LineOfCreditFacilityAggregateRevolvingLenderCommitments_019fecad-8bc0-70b4-8b3e-f5d9817a1f98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermLineOfCredit_019fecad-8bc0-7128-93cb-85a5c2a69c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermLineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LongTermLineOfCredit_019fecad-8bc0-7128-93cb-85a5c2a69c9b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_019fecad-8bc0-71a0-9c53-868e6e256fd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_019fecad-8bc0-71a0-9c53-868e6e256fd2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019fecad-8bc0-7d41-95e6-1db09a67ce92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019fecad-8bc0-7d41-95e6-1db09a67ce92" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019fecad-8bc0-7930-92d0-f8b5b3423792" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019fecad-8bc0-7930-92d0-f8b5b3423792" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_019fecad-8bc0-718b-b855-fdc3dfadd3de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019fecad-8bc0-71dd-9ded-20faa72ddd93" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_019fecad-8bc0-718b-b855-fdc3dfadd3de" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/SeniorNotesDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#SeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/SeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7dcd-b650-5390151df4c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7dcd-b650-5390151df4c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-729d-b41a-c3630ee746d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7dcd-b650-5390151df4c6" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-729d-b41a-c3630ee746d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-729d-b41a-c3630ee746d1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-729d-b41a-c3630ee746d1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-729d-b41a-c3630ee746d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-729d-b41a-c3630ee746d1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A5.000SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-7c95-9575-7447fcab8bf8" xlink:href="sm-20260930.xsd#sm_A5.000SeniorUnsecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A5.000SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-7c95-9575-7447fcab8bf8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-753d-af1f-eca02a8a4073" xlink:href="sm-20260930.xsd#sm_A6.75SeniorUnsecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-753d-af1f-eca02a8a4073" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_019fecad-8bc0-771c-80f2-8a523e6fd8d2" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_019fecad-8bc0-771c-80f2-8a523e6fd8d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7b52-a465-0c542518654b" xlink:href="sm-20260930.xsd#sm_A8.375SeniorUnsecuredNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7b52-a465-0c542518654b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.5SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7b8e-ba46-46c070fbf70c" xlink:href="sm-20260930.xsd#sm_A6.5SeniorUnsecuredNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A6.5SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7b8e-ba46-46c070fbf70c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.75SeniorUnsecuredNotesDue2029Member_019fecad-8bc0-7208-94ef-c19c8a56c9b7" xlink:href="sm-20260930.xsd#sm_A6.75SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A6.75SeniorUnsecuredNotesDue2029Member_019fecad-8bc0-7208-94ef-c19c8a56c9b7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.625SeniorUnsecuredNotesDue2030Member_019fecad-8bc0-76e7-8c26-ba68d1490b9f" xlink:href="sm-20260930.xsd#sm_A8.625SeniorUnsecuredNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A8.625SeniorUnsecuredNotesDue2030Member_019fecad-8bc0-76e7-8c26-ba68d1490b9f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.750SeniorUnsecuredNotesDue2031Member_019fecad-8bc0-7a18-a7a4-2e3bb3d45a06" xlink:href="sm-20260930.xsd#sm_A8.750SeniorUnsecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A8.750SeniorUnsecuredNotesDue2031Member_019fecad-8bc0-7a18-a7a4-2e3bb3d45a06" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A7.0SeniorUnsecuredNotesDue2032Member_019fecad-8bc0-7c9c-b196-bb5a71258c2a" xlink:href="sm-20260930.xsd#sm_A7.0SeniorUnsecuredNotesDue2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A7.0SeniorUnsecuredNotesDue2032Member_019fecad-8bc0-7c9c-b196-bb5a71258c2a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A9.625SeniorUnsecuredNotesDue2033Member_019fecad-8bc0-717e-8a90-02879d8db7db" xlink:href="sm-20260930.xsd#sm_A9.625SeniorUnsecuredNotesDue2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A9.625SeniorUnsecuredNotesDue2033Member_019fecad-8bc0-717e-8a90-02879d8db7db" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-737a-a036-4e96acea7e02" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-737a-a036-4e96acea7e02" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019fecad-8bc0-7c9e-a8be-22cc998b6b3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7738-ae83-84d168893a4b" xlink:to="loc_us-gaap_SeniorNotesMember_019fecad-8bc0-7c9e-a8be-22cc998b6b3e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7dcd-b650-5390151df4c6" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-77f8-8638-5bf2bd71a332" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-7ff9-a7aa-2ba4ad336f98" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-77f8-8638-5bf2bd71a332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7c23-8094-82cbb2b91fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-77f8-8638-5bf2bd71a332" xlink:to="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7c23-8094-82cbb2b91fa0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fecad-8bc0-72c3-8a60-f8d1289cf32a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fecad-8bc0-72c3-8a60-f8d1289cf32a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-73a0-bf59-dc12cabcde7d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-73a0-bf59-dc12cabcde7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedPremium_019fecad-8bc0-74ad-89a4-c439d1e757ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedPremium_019fecad-8bc0-74ad-89a4-c439d1e757ea" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_019fecad-8bc0-7aba-bc85-9eb355809bde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_019fecad-8bc0-7aba-bc85-9eb355809bde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019fecad-8bc0-7ff6-8456-f31701bebff0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_SeniorNotes_019fecad-8bc0-7ff6-8456-f31701bebff0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentIssuanceDate1_019fecad-8bc0-7bd5-9514-6c0559d915b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentIssuanceDate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentIssuanceDate1_019fecad-8bc0-7bd5-9514-6c0559d915b0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_019fecad-8bc0-714b-a344-6d2b5c5a0f95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_019fecad-8bc0-714b-a344-6d2b5c5a0f95" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_019fecad-8bc0-7a0d-92dc-a4554d192f6a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromDebtNetOfIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7c83-a911-8bb85d171545" xlink:to="loc_us-gaap_ProceedsFromDebtNetOfIssuanceCosts_019fecad-8bc0-7a0d-92dc-a4554d192f6a" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/LongTermDebtDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#LongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/LongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7d90-b748-1f97606ed09a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7d90-b748-1f97606ed09a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-75ab-b5f1-4514f26fa445" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7d90-b748-1f97606ed09a" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-75ab-b5f1-4514f26fa445" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-75ab-b5f1-4514f26fa445_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-75ab-b5f1-4514f26fa445" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-75ab-b5f1-4514f26fa445_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7a92-89b5-1d629d23991c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fecad-8bc0-75ab-b5f1-4514f26fa445" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7a92-89b5-1d629d23991c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7b9e-8227-327c90b3b7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019fecad-8bc0-7a92-89b5-1d629d23991c" xlink:to="loc_us-gaap_SubsequentEventMember_019fecad-8bc0-7b9e-8227-327c90b3b7b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7895-931e-ea3056554113" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7d90-b748-1f97606ed09a" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7895-931e-ea3056554113" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7895-931e-ea3056554113_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7895-931e-ea3056554113" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7895-931e-ea3056554113_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7895-931e-ea3056554113" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-7044-bc72-9a7b555cf6df" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-7044-bc72-9a7b555cf6df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-76d5-822f-a1de9f15879b" xlink:href="sm-20260930.xsd#sm_A8.375SeniorUnsecuredNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:to="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-76d5-822f-a1de9f15879b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A5.000SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-78f9-96e0-ab736b986529" xlink:href="sm-20260930.xsd#sm_A5.000SeniorUnsecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:to="loc_sm_A5.000SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-78f9-96e0-ab736b986529" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-75e3-bc3b-5f13d48ffd64" xlink:href="sm-20260930.xsd#sm_A6.75SeniorUnsecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:to="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-75e3-bc3b-5f13d48ffd64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_01a049d9-3bab-721e-b993-8550c25f7165" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7213-a583-69ab7a555d29" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_01a049d9-3bab-721e-b993-8550c25f7165" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-72d1-a5d0-67a7e025c20b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019fecad-8bc0-7d90-b748-1f97606ed09a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-72d1-a5d0-67a7e025c20b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-72d1-a5d0-67a7e025c20b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-72d1-a5d0-67a7e025c20b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-72d1-a5d0-67a7e025c20b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-76b0-ba67-9fa3675ae977" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-72d1-a5d0-67a7e025c20b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-76b0-ba67-9fa3675ae977" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-72f2-af4c-c248a40e4093" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-76b0-ba67-9fa3675ae977" xlink:to="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-72f2-af4c-c248a40e4093" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_SeniorNotesAssumedPrincipal_019fecad-8bc0-7754-a951-1f6991a2b68c" xlink:href="sm-20260930.xsd#sm_SeniorNotesAssumedPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_sm_SeniorNotesAssumedPrincipal_019fecad-8bc0-7754-a951-1f6991a2b68c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_AssumedCreditFacilityDebtRepaid_019fecad-8bc0-7550-977e-7160cdcf774e" xlink:href="sm-20260930.xsd#sm_AssumedCreditFacilityDebtRepaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_sm_AssumedCreditFacilityDebtRepaid_019fecad-8bc0-7550-977e-7160cdcf774e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_019fecad-8bc0-7530-b46c-88379131b199" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_019fecad-8bc0-7530-b46c-88379131b199" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_019fecad-8bc0-7a8c-a1e9-a22aebc6d341" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_019fecad-8bc0-7a8c-a1e9-a22aebc6d341" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_019fecad-8bc0-7fa6-8ef6-28dea6adf46a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_019fecad-8bc0-7fa6-8ef6-28dea6adf46a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019fecad-8bc0-785d-8ccb-bff31d63c845" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_019fecad-8bc0-785d-8ccb-bff31d63c845" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-7ee8-afea-b3ffe4cf0721" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-7ee8-afea-b3ffe4cf0721" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019fecad-8bc0-77b6-9d7d-32ea8a92202c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019fecad-8bc0-77b6-9d7d-32ea8a92202c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCovenantCompliance_019fecad-8bc0-7c73-97e5-47918aa0d289" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCovenantCompliance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_DebtInstrumentCovenantCompliance_019fecad-8bc0-7c73-97e5-47918aa0d289" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalized_019fecad-8bc0-7748-8094-4480fad670e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestCostsCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019fecad-8bc0-7631-8fe8-2262176073c9" xlink:to="loc_us-gaap_InterestCostsCapitalized_019fecad-8bc0-7748-8094-4480fad670e2" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/CommitmentsDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#CommitmentsDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/CommitmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_019fecad-8bc0-7a96-bcfe-2c1bbcb5aaa9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:to="loc_us-gaap_OtherCommitmentsTable_019fecad-8bc0-7a96-bcfe-2c1bbcb5aaa9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019fecad-8bc0-780f-a787-218ab9d0b7b1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_019fecad-8bc0-7a96-bcfe-2c1bbcb5aaa9" xlink:to="loc_srt_RangeAxis_019fecad-8bc0-780f-a787-218ab9d0b7b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fecad-8bc0-780f-a787-218ab9d0b7b1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019fecad-8bc0-780f-a787-218ab9d0b7b1" xlink:to="loc_srt_RangeMember_019fecad-8bc0-780f-a787-218ab9d0b7b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019fecad-8bc0-77ae-be90-19b45008de69" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019fecad-8bc0-780f-a787-218ab9d0b7b1" xlink:to="loc_srt_RangeMember_019fecad-8bc0-77ae-be90-19b45008de69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019fecad-8bc0-7ea3-9b35-3334ea106ac3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fecad-8bc0-77ae-be90-19b45008de69" xlink:to="loc_srt_MinimumMember_019fecad-8bc0-7ea3-9b35-3334ea106ac3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019fecad-8bc0-7a1c-8d26-3b8cf729dafa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019fecad-8bc0-77ae-be90-19b45008de69" xlink:to="loc_srt_MaximumMember_019fecad-8bc0-7a1c-8d26-3b8cf729dafa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019fecad-8bc0-7449-82cf-3df59c582d5a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_019fecad-8bc0-7a96-bcfe-2c1bbcb5aaa9" xlink:to="loc_srt_StatementScenarioAxis_019fecad-8bc0-7449-82cf-3df59c582d5a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019fecad-8bc0-7449-82cf-3df59c582d5a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019fecad-8bc0-7449-82cf-3df59c582d5a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019fecad-8bc0-7449-82cf-3df59c582d5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019fecad-8bc0-7ee3-bd69-85cfe483331b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019fecad-8bc0-7449-82cf-3df59c582d5a" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019fecad-8bc0-7ee3-bd69-85cfe483331b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_019fecad-8bc0-7244-aa1f-7cd32dfd7626" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019fecad-8bc0-7ee3-bd69-85cfe483331b" xlink:to="loc_srt_ScenarioForecastMember_019fecad-8bc0-7244-aa1f-7cd32dfd7626" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DrillingAndCompletionCommitmentLiquidatedDamagesPotential_019fecad-8bc0-7256-8550-31e2c8f305b4" xlink:href="sm-20260930.xsd#sm_DrillingAndCompletionCommitmentLiquidatedDamagesPotential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:to="loc_sm_DrillingAndCompletionCommitmentLiquidatedDamagesPotential_019fecad-8bc0-7256-8550-31e2c8f305b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OtherCommitmentNumberOfWellsRequiredToDrillAndComplete_019fecad-8bc0-7cc6-a698-c5d59b4dd5b7" xlink:href="sm-20260930.xsd#sm_OtherCommitmentNumberOfWellsRequiredToDrillAndComplete"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:to="loc_sm_OtherCommitmentNumberOfWellsRequiredToDrillAndComplete_019fecad-8bc0-7cc6-a698-c5d59b4dd5b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_SupplyCommitmentEnergyRequiredToDeliver_019fecad-8bc0-7fcf-92dd-ab7078973b1d" xlink:href="sm-20260930.xsd#sm_SupplyCommitmentEnergyRequiredToDeliver"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:to="loc_sm_SupplyCommitmentEnergyRequiredToDeliver_019fecad-8bc0-7fcf-92dd-ab7078973b1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_SupplyCommitmentAggregateUndiscountedDeficiencyPaymentsUponFailureToDeliverProduct_019fecad-8bc0-759d-bc67-4d0d6d888c1b" xlink:href="sm-20260930.xsd#sm_SupplyCommitmentAggregateUndiscountedDeficiencyPaymentsUponFailureToDeliverProduct"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_019fecad-8bc0-712b-b6de-f312b12cef8d" xlink:to="loc_sm_SupplyCommitmentAggregateUndiscountedDeficiencyPaymentsUponFailureToDeliverProduct_019fecad-8bc0-759d-bc67-4d0d6d888c1b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/DerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#DerivativeFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/DerivativeFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019fecad-8bc0-7e09-8a37-e96a8cc417bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeTable_019fecad-8bc0-7e09-8a37-e96a8cc417bc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeUnderlyingIndexAxis_019fecad-8bc0-72af-838c-0099f6ef5ea1" xlink:href="sm-20260930.xsd#sm_DerivativeUnderlyingIndexAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019fecad-8bc0-7e09-8a37-e96a8cc417bc" xlink:to="loc_sm_DerivativeUnderlyingIndexAxis_019fecad-8bc0-72af-838c-0099f6ef5ea1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-72af-838c-0099f6ef5ea1_default" xlink:href="sm-20260930.xsd#sm_DerivativeUnderlyingIndexDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_sm_DerivativeUnderlyingIndexAxis_019fecad-8bc0-72af-838c-0099f6ef5ea1" xlink:to="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-72af-838c-0099f6ef5ea1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:href="sm-20260930.xsd#sm_DerivativeUnderlyingIndexDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_sm_DerivativeUnderlyingIndexAxis_019fecad-8bc0-72af-838c-0099f6ef5ea1" xlink:to="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_WTIMidlandNYMEXWTIMember_019fecad-8bc0-7d14-85de-8581904d9a22" xlink:href="sm-20260930.xsd#sm_WTIMidlandNYMEXWTIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_WTIMidlandNYMEXWTIMember_019fecad-8bc0-7d14-85de-8581904d9a22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_WTIHoustonMEHNYMEXWTIMember_019fecad-8bc0-7087-bc86-24167d441435" xlink:href="sm-20260930.xsd#sm_WTIHoustonMEHNYMEXWTIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_WTIHoustonMEHNYMEXWTIMember_019fecad-8bc0-7087-bc86-24167d441435" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXHHMember_019fecad-8bc0-7d90-a5bb-3367ca5be439" xlink:href="sm-20260930.xsd#sm_NYMEXHHMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_NYMEXHHMember_019fecad-8bc0-7d90-a5bb-3367ca5be439" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_IFWAHAMember_019fecad-8bc0-78d3-9da2-910f299b69d9" xlink:href="sm-20260930.xsd#sm_IFWAHAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_IFWAHAMember_019fecad-8bc0-78d3-9da2-910f299b69d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_IFWAHANYMEXHHMember_019fecad-8bc0-7913-8bd7-cc0140ebd839" xlink:href="sm-20260930.xsd#sm_IFWAHANYMEXHHMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_IFWAHANYMEXHHMember_019fecad-8bc0-7913-8bd7-cc0140ebd839" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CIGRockiesNYMEXHHMember_019fecad-8bc0-7b0a-a56e-98df52485f9a" xlink:href="sm-20260930.xsd#sm_CIGRockiesNYMEXHHMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_CIGRockiesNYMEXHHMember_019fecad-8bc0-7b0a-a56e-98df52485f9a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OPISEthaneMontBelvieuNonTETMember_019fecad-8bc0-7b79-8da6-55f90c7f5888" xlink:href="sm-20260930.xsd#sm_OPISEthaneMontBelvieuNonTETMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sm_DerivativeUnderlyingIndexDomain_019fecad-8bc0-75a4-a5f3-002f9aac815c" xlink:to="loc_sm_OPISEthaneMontBelvieuNonTETMember_019fecad-8bc0-7b79-8da6-55f90c7f5888" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-78f7-bbd4-4eaba07990ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019fecad-8bc0-7e09-8a37-e96a8cc417bc" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-78f7-bbd4-4eaba07990ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f7-bbd4-4eaba07990ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-78f7-bbd4-4eaba07990ca" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f7-bbd4-4eaba07990ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-78f7-bbd4-4eaba07990ca" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilSwapContractFourthQuarterYear1Member_019fecad-8bc0-78c0-85fb-8000a606e467" xlink:href="sm-20260930.xsd#sm_NYMEXOilSwapContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilSwapContractFourthQuarterYear1Member_019fecad-8bc0-78c0-85fb-8000a606e467" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilSwapContractYear2Member_019fecad-8bc0-7fc9-a516-e11897644ce2" xlink:href="sm-20260930.xsd#sm_NYMEXOilSwapContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilSwapContractYear2Member_019fecad-8bc0-7fc9-a516-e11897644ce2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilSwapContractYear3Member_019fecad-8bc0-7139-9849-36ac7d703373" xlink:href="sm-20260930.xsd#sm_NYMEXOilSwapContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilSwapContractYear3Member_019fecad-8bc0-7139-9849-36ac7d703373" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCollarContractFourthQuarterYear1Member_019fecad-8bc0-7b07-8153-7464dee81666" xlink:href="sm-20260930.xsd#sm_NYMEXOilCollarContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCollarContractFourthQuarterYear1Member_019fecad-8bc0-7b07-8153-7464dee81666" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCollarContractYear2Member_019fecad-8bc0-774b-954c-b162a4781d2b" xlink:href="sm-20260930.xsd#sm_NYMEXOilCollarContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCollarContractYear2Member_019fecad-8bc0-774b-954c-b162a4781d2b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCollarContractYear3Member_019fecad-8bc0-742a-8f5f-c4b3ff1a3c59" xlink:href="sm-20260930.xsd#sm_NYMEXOilCollarContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCollarContractYear3Member_019fecad-8bc0-742a-8f5f-c4b3ff1a3c59" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OilBasisSwapContractFourthQuarterYear1Member_019fecad-8bc0-741b-acde-8e1540e67683" xlink:href="sm-20260930.xsd#sm_OilBasisSwapContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_OilBasisSwapContractFourthQuarterYear1Member_019fecad-8bc0-741b-acde-8e1540e67683" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OilBasisSwapContractYear2Member_019fecad-8bc0-7ba8-89a7-ab68f19268a0" xlink:href="sm-20260930.xsd#sm_OilBasisSwapContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_OilBasisSwapContractYear2Member_019fecad-8bc0-7ba8-89a7-ab68f19268a0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OilBasisSwapContractYear3Member_019fecad-8bc0-7526-b2a1-3855d6242985" xlink:href="sm-20260930.xsd#sm_OilBasisSwapContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_OilBasisSwapContractYear3Member_019fecad-8bc0-7526-b2a1-3855d6242985" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractFourthQuarterYear1Member_019fecad-8bc0-7c0e-b00a-9d621b6c166d" xlink:href="sm-20260930.xsd#sm_NYMEXOilCalendarMonthAverageRollDifferentialContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractFourthQuarterYear1Member_019fecad-8bc0-7c0e-b00a-9d621b6c166d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear2Member_019fecad-8bc0-717f-bcb8-0ac5680cce4f" xlink:href="sm-20260930.xsd#sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear2Member_019fecad-8bc0-717f-bcb8-0ac5680cce4f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear3Member_019fecad-8bc0-735e-a2b0-e724ffcb32f0" xlink:href="sm-20260930.xsd#sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NYMEXOilCalendarMonthAverageRollDifferentialContractYear3Member_019fecad-8bc0-735e-a2b0-e724ffcb32f0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasSwapsContractFourthQuarterYear1Member_019fecad-8bc0-7d62-90eb-75563d68661a" xlink:href="sm-20260930.xsd#sm_GasSwapsContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasSwapsContractFourthQuarterYear1Member_019fecad-8bc0-7d62-90eb-75563d68661a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasSwapsContractYear2Member_019fecad-8bc0-7d56-a808-c8623a78f0b1" xlink:href="sm-20260930.xsd#sm_GasSwapsContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasSwapsContractYear2Member_019fecad-8bc0-7d56-a808-c8623a78f0b1" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasSwapsContractYear3Member_019fecad-8bc0-7f77-970a-2aeae05b1c2f" xlink:href="sm-20260930.xsd#sm_GasSwapsContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasSwapsContractYear3Member_019fecad-8bc0-7f77-970a-2aeae05b1c2f" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasCollarContractFourthQuarterYear1Member_019fecad-8bc0-7513-987a-8c07e387e046" xlink:href="sm-20260930.xsd#sm_GasCollarContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasCollarContractFourthQuarterYear1Member_019fecad-8bc0-7513-987a-8c07e387e046" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasCollarContractYear2Member_019fecad-8bc0-7287-aa8a-ddafcc54a8f8" xlink:href="sm-20260930.xsd#sm_GasCollarContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasCollarContractYear2Member_019fecad-8bc0-7287-aa8a-ddafcc54a8f8" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasCollarContractYear3Member_019fecad-8bc0-7a67-bb68-0abd6936f156" xlink:href="sm-20260930.xsd#sm_GasCollarContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasCollarContractYear3Member_019fecad-8bc0-7a67-bb68-0abd6936f156" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasBasisSwapContractFourthQuarterYear1Member_019fecad-8bc0-7aa8-8dcd-12cdf475e0b6" xlink:href="sm-20260930.xsd#sm_GasBasisSwapContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasBasisSwapContractFourthQuarterYear1Member_019fecad-8bc0-7aa8-8dcd-12cdf475e0b6" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasBasisSwapContractYear2Member_019fecad-8bc0-71e8-9274-d77304ff9226" xlink:href="sm-20260930.xsd#sm_GasBasisSwapContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasBasisSwapContractYear2Member_019fecad-8bc0-71e8-9274-d77304ff9226" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasBasisSwapContractYear3Member_019fecad-8bc0-7f0a-b690-62e7ce499d3f" xlink:href="sm-20260930.xsd#sm_GasBasisSwapContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_GasBasisSwapContractYear3Member_019fecad-8bc0-7f0a-b690-62e7ce499d3f" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NGLSwapsContractFourthQuarterYear1Member_019fecad-8bc0-7778-8d7b-b2503fa867bf" xlink:href="sm-20260930.xsd#sm_NGLSwapsContractFourthQuarterYear1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NGLSwapsContractFourthQuarterYear1Member_019fecad-8bc0-7778-8d7b-b2503fa867bf" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NGLSwapsContractYear2Member_019fecad-8bc0-7e04-ad20-9d7c11151b6c" xlink:href="sm-20260930.xsd#sm_NGLSwapsContractYear2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NGLSwapsContractYear2Member_019fecad-8bc0-7e04-ad20-9d7c11151b6c" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NGLSwapsContractYear3Member_019fecad-8bc0-7ffb-83a1-9307bc7f96c1" xlink:href="sm-20260930.xsd#sm_NGLSwapsContractYear3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-78f8-b27f-f0ded38302f4" xlink:to="loc_sm_NGLSwapsContractYear3Member_019fecad-8bc0-7ffb-83a1-9307bc7f96c1" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNonmonetaryNotionalAmountVolume_019fecad-8bc0-7266-b6d7-a808e544bcd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNonmonetaryNotionalAmountVolume"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeNonmonetaryNotionalAmountVolume_019fecad-8bc0-7266-b6d7-a808e544bcd0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure_019fecad-8bc0-7310-b5b1-4eb027c7871d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure_019fecad-8bc0-7310-b5b1-4eb027c7871d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeSwapTypeAverageFixedPrice_019fecad-8bc0-76d8-ae6c-2e0e82c6443c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeSwapTypeAverageFixedPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeSwapTypeAverageFixedPrice_019fecad-8bc0-76d8-ae6c-2e0e82c6443c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFloorPrice_019fecad-8bc0-7260-b0d8-8275a83d5ff1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFloorPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeFloorPrice_019fecad-8bc0-7260-b0d8-8275a83d5ff1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCapPrice_019fecad-8bc0-7f1d-ad15-c52c6b91904a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeCapPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_us-gaap_DerivativeCapPrice_019fecad-8bc0-7f1d-ad15-c52c6b91904a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeOilBasisSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7330-ad06-26be14b42d03" xlink:href="sm-20260930.xsd#sm_DerivativeOilBasisSwapTypeWeightedAverageContractPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_sm_DerivativeOilBasisSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7330-ad06-26be14b42d03" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeCalendarMonthAverageRollDifferentialSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7a95-b19e-9f8e1fa9fa75" xlink:href="sm-20260930.xsd#sm_DerivativeCalendarMonthAverageRollDifferentialSwapTypeWeightedAverageContractPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_sm_DerivativeCalendarMonthAverageRollDifferentialSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7a95-b19e-9f8e1fa9fa75" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeGasBasisSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7387-9dfd-cba4fb624e22" xlink:href="sm-20260930.xsd#sm_DerivativeGasBasisSwapTypeWeightedAverageContractPrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019fecad-8bc0-7812-8ddc-821e29f55ebd" xlink:to="loc_sm_DerivativeGasBasisSwapTypeWeightedAverageContractPrice_019fecad-8bc0-7387-9dfd-cba4fb624e22" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/DerivativeFinancialInstrumentsFairValueDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#DerivativeFinancialInstrumentsFairValueDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/DerivativeFinancialInstrumentsFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019fecad-8bc0-718a-919d-8344dbef73fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019fecad-8bc0-718a-919d-8344dbef73fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-7168-8c24-2d120b777839" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019fecad-8bc0-718a-919d-8344dbef73fe" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-7168-8c24-2d120b777839" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-7168-8c24-2d120b777839_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-7168-8c24-2d120b777839" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-7168-8c24-2d120b777839_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-7e02-87ce-8b07b38211b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-7168-8c24-2d120b777839" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-7e02-87ce-8b07b38211b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019fecad-8bc0-775c-a99a-dd3f112e7ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-7e02-87ce-8b07b38211b3" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019fecad-8bc0-775c-a99a-dd3f112e7ef1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7619-a547-a89b7635abd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019fecad-8bc0-718a-919d-8344dbef73fe" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7619-a547-a89b7635abd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7619-a547-a89b7635abd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7619-a547-a89b7635abd4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7619-a547-a89b7635abd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-703b-b270-ddce12811dad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7619-a547-a89b7635abd4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-703b-b270-ddce12811dad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019fecad-8bc0-75cb-b217-04ce26658dec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-703b-b270-ddce12811dad" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019fecad-8bc0-75cb-b217-04ce26658dec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-76d6-bfeb-8b0563511e48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019fecad-8bc0-718a-919d-8344dbef73fe" xlink:to="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-76d6-bfeb-8b0563511e48" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-76d6-bfeb-8b0563511e48_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-76d6-bfeb-8b0563511e48" xlink:to="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-76d6-bfeb-8b0563511e48_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7d33-a571-f9bc009f8115" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-76d6-bfeb-8b0563511e48" xlink:to="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7d33-a571-f9bc009f8115" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019fecad-8bc0-724e-9d6b-e1a35503ee84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7d33-a571-f9bc009f8115" xlink:to="loc_us-gaap_NondesignatedMember_019fecad-8bc0-724e-9d6b-e1a35503ee84" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019fecad-8bc0-7718-98e9-45fbaf039e7d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_019fecad-8bc0-7718-98e9-45fbaf039e7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_019fecad-8bc0-7c53-b81c-e23d23b86c4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_019fecad-8bc0-7c53-b81c-e23d23b86c4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_019fecad-8bc0-7cc8-892c-7c655b0e7eef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_019fecad-8bc0-7cc8-892c-7c655b0e7eef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019fecad-8bc0-754a-989b-f4126231224a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019fecad-8bc0-754a-989b-f4126231224a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_019fecad-8bc0-7282-b722-b2f177ade545" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_019fecad-8bc0-7282-b722-b2f177ade545" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019fecad-8bc0-7a5a-b460-4c70ef028efe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_019fecad-8bc0-7a5a-b460-4c70ef028efe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019fecad-8bc0-7ae8-ad98-0c32fd12ed99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019fecad-8bc0-7ae8-ad98-0c32fd12ed99" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction_019fecad-8bc0-7f09-a923-1b7335c25e99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction_019fecad-8bc0-7f09-a923-1b7335c25e99" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction_019fecad-8bc0-7730-a231-9ef987f26735" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction_019fecad-8bc0-7730-a231-9ef987f26735" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019fecad-8bc0-7ee0-bfe9-f5d4e4000824" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral_019fecad-8bc0-7ee0-bfe9-f5d4e4000824" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_019fecad-8bc0-7194-bba0-4c988539c665" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019fecad-8bc0-7625-86e2-a9153aea3084" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral_019fecad-8bc0-7194-bba0-4c988539c665" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/DerivativeFinancialInstrumentsGainsandLossesDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#DerivativeFinancialInstrumentsGainsandLossesDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/DerivativeFinancialInstrumentsGainsandLossesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019fecad-8bc0-744a-8a33-8cb9fddc7151" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019fecad-8bc0-7efc-addc-f198249cf260" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019fecad-8bc0-744a-8a33-8cb9fddc7151" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019fecad-8bc0-7efc-addc-f198249cf260" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-7794-b946-9daa6c280222" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019fecad-8bc0-7efc-addc-f198249cf260" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-7794-b946-9daa6c280222" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7794-b946-9daa6c280222_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-7794-b946-9daa6c280222" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7794-b946-9daa6c280222_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7102-8d3f-98965ec01a13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fecad-8bc0-7794-b946-9daa6c280222" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7102-8d3f-98965ec01a13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_OilContractsMember_019fecad-8bc0-7c88-a220-8f9f42ef21a9" xlink:href="sm-20260930.xsd#sm_OilContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7102-8d3f-98965ec01a13" xlink:to="loc_sm_OilContractsMember_019fecad-8bc0-7c88-a220-8f9f42ef21a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_GasContractsMember_019fecad-8bc0-74fa-ab3b-a6ceb5315b9f" xlink:href="sm-20260930.xsd#sm_GasContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7102-8d3f-98965ec01a13" xlink:to="loc_sm_GasContractsMember_019fecad-8bc0-74fa-ab3b-a6ceb5315b9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_NGLContractsMember_019fecad-8bc0-72ea-ba4b-2ee624c182d9" xlink:href="sm-20260930.xsd#sm_NGLContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fecad-8bc0-7102-8d3f-98965ec01a13" xlink:to="loc_sm_NGLContractsMember_019fecad-8bc0-72ea-ba4b-2ee624c182d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_DerivativeSettlementGainOrLoss_019fecad-8bc0-7817-82e8-2adc79fb7868" xlink:href="sm-20260930.xsd#sm_DerivativeSettlementGainOrLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019fecad-8bc0-744a-8a33-8cb9fddc7151" xlink:to="loc_sm_DerivativeSettlementGainOrLoss_019fecad-8bc0-7817-82e8-2adc79fb7868" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019fecad-8bc0-7810-9bfd-6b8a2121dca4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019fecad-8bc0-744a-8a33-8cb9fddc7151" xlink:to="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019fecad-8bc0-7810-9bfd-6b8a2121dca4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/FairValueDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#FairValueDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/FairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019fecad-8bc0-7555-8ed4-746876e6c9c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019fecad-8bc0-7555-8ed4-746876e6c9c8" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-7c5a-bfad-71464c733d75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:to="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-7c5a-bfad-71464c733d75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7c5a-bfad-71464c733d75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-7c5a-bfad-71464c733d75" xlink:to="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7c5a-bfad-71464c733d75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7adb-a25c-45e608c3f1cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019fecad-8bc0-7c5a-bfad-71464c733d75" xlink:to="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7adb-a25c-45e608c3f1cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019fecad-8bc0-74f8-9fb9-90edac9b1ea8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019fecad-8bc0-7adb-a25c-45e608c3f1cd" xlink:to="loc_us-gaap_NondesignatedMember_019fecad-8bc0-74f8-9fb9-90edac9b1ea8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-79d0-82f4-109d0e3c5f4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-79d0-82f4-109d0e3c5f4e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-79d0-82f4-109d0e3c5f4e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-79d0-82f4-109d0e3c5f4e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-79d0-82f4-109d0e3c5f4e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-72fa-a70d-bc2c67b6c2ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019fecad-8bc0-79d0-82f4-109d0e3c5f4e" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-72fa-a70d-bc2c67b6c2ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019fecad-8bc0-780b-b2c8-9e9a69383a88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019fecad-8bc0-72fa-a70d-bc2c67b6c2ce" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019fecad-8bc0-780b-b2c8-9e9a69383a88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7bfb-a736-04394d9f19c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7bfb-a736-04394d9f19c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7bfb-a736-04394d9f19c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7bfb-a736-04394d9f19c5" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7bfb-a736-04394d9f19c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7304-9e63-c2129fc1e499" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019fecad-8bc0-7bfb-a736-04394d9f19c5" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7304-9e63-c2129fc1e499" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019fecad-8bc0-73b1-9d19-371a78b68515" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7304-9e63-c2129fc1e499" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019fecad-8bc0-73b1-9d19-371a78b68515" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019fecad-8bc0-7bb3-b25d-5d46f9186f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7304-9e63-c2129fc1e499" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019fecad-8bc0-7bb3-b25d-5d46f9186f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019fecad-8bc0-7d3c-abdf-cb68f94a957e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019fecad-8bc0-7304-9e63-c2129fc1e499" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019fecad-8bc0-7d3c-abdf-cb68f94a957e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7151-96be-e2b28699f7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019fecad-8bc0-7cae-bc91-ee41a7437631" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7151-96be-e2b28699f7ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7151-96be-e2b28699f7ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7151-96be-e2b28699f7ba" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7151-96be-e2b28699f7ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fecad-8bc0-7151-96be-e2b28699f7ba" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-7254-9079-c9dc9e62d781" xlink:href="sm-20260930.xsd#sm_A6.75SeniorUnsecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A6.75SeniorUnsecuredNotesDue2026Member_019fecad-8bc0-7254-9079-c9dc9e62d781" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_019fecad-8bc0-7074-99f6-fb48d397d732" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2027Member_019fecad-8bc0-7074-99f6-fb48d397d732" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7e5c-90af-34b8420525e0" xlink:href="sm-20260930.xsd#sm_A8.375SeniorUnsecuredNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A8.375SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-7e5c-90af-34b8420525e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.5SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-755a-b3c6-12600deb166f" xlink:href="sm-20260930.xsd#sm_A6.5SeniorUnsecuredNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A6.5SeniorUnsecuredNotesDue2028Member_019fecad-8bc0-755a-b3c6-12600deb166f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.75SeniorUnsecuredNotesDue2029Member_019fecad-8bc0-7ad7-9d57-a1f0f9ae5647" xlink:href="sm-20260930.xsd#sm_A6.75SeniorUnsecuredNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A6.75SeniorUnsecuredNotesDue2029Member_019fecad-8bc0-7ad7-9d57-a1f0f9ae5647" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.625SeniorUnsecuredNotesDue2030Member_019fecad-8bc0-70ba-b290-05293b2fae9a" xlink:href="sm-20260930.xsd#sm_A8.625SeniorUnsecuredNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A8.625SeniorUnsecuredNotesDue2030Member_019fecad-8bc0-70ba-b290-05293b2fae9a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A8.750SeniorUnsecuredNotesDue2031Member_019fecad-8bc0-7f49-97f0-800de87c363c" xlink:href="sm-20260930.xsd#sm_A8.750SeniorUnsecuredNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A8.750SeniorUnsecuredNotesDue2031Member_019fecad-8bc0-7f49-97f0-800de87c363c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A7.0SeniorUnsecuredNotesDue2032Member_019fecad-8bc0-7d2a-8396-f41ed751178b" xlink:href="sm-20260930.xsd#sm_A7.0SeniorUnsecuredNotesDue2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A7.0SeniorUnsecuredNotesDue2032Member_019fecad-8bc0-7d2a-8396-f41ed751178b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A9.625SeniorUnsecuredNotesDue2033Member_019fecad-8bc0-7772-944a-f3e1d24c5bde" xlink:href="sm-20260930.xsd#sm_A9.625SeniorUnsecuredNotesDue2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A9.625SeniorUnsecuredNotesDue2033Member_019fecad-8bc0-7772-944a-f3e1d24c5bde" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-7a9a-8b57-9fce8a68a596" xlink:href="sm-20260930.xsd#sm_A6.625SeniorUnsecuredNotesDue2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fecad-8bc0-7f88-a064-ebf4a65f548d" xlink:to="loc_sm_A6.625SeniorUnsecuredNotesDue2034Member_019fecad-8bc0-7a9a-8b57-9fce8a68a596" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019fecad-8bc0-7133-a300-8ad404941c8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019fecad-8bc0-7555-8ed4-746876e6c9c8" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019fecad-8bc0-7133-a300-8ad404941c8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019fecad-8bc0-78f0-ab63-90893dedeb06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019fecad-8bc0-7133-a300-8ad404941c8e" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019fecad-8bc0-78f0-ab63-90893dedeb06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019fecad-8bc0-78a1-9104-6921fb9d25a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019fecad-8bc0-7555-8ed4-746876e6c9c8" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019fecad-8bc0-78a1-9104-6921fb9d25a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019fecad-8bc0-711c-82ae-44f63eb52acc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019fecad-8bc0-78a1-9104-6921fb9d25a0" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019fecad-8bc0-711c-82ae-44f63eb52acc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValueDisclosureAbstract_019fecad-8bc0-746a-b18b-b9e882bf6ce4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019fecad-8bc0-7555-8ed4-746876e6c9c8" xlink:to="loc_us-gaap_DebtInstrumentFairValueDisclosureAbstract_019fecad-8bc0-746a-b18b-b9e882bf6ce4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fecad-8bc0-7816-b57b-cdff83e83a8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentFairValueDisclosureAbstract_019fecad-8bc0-746a-b18b-b9e882bf6ce4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fecad-8bc0-7816-b57b-cdff83e83a8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-7a2c-9e68-9c613d78eb49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentFairValueDisclosureAbstract_019fecad-8bc0-746a-b18b-b9e882bf6ce4" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019fecad-8bc0-7a2c-9e68-9c613d78eb49" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019fecad-8bc0-70f6-beb8-37f89513711c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentFairValueDisclosureAbstract_019fecad-8bc0-746a-b18b-b9e882bf6ce4" xlink:to="loc_us-gaap_LongTermDebtFairValue_019fecad-8bc0-70f6-beb8-37f89513711c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/SegmentReportingDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#SegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/SegmentReportingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-74c7-a99a-f11e1ce86ad3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-74c7-a99a-f11e1ce86ad3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019fecad-8bc0-76c3-a3ce-8f71f659ea5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-74c7-a99a-f11e1ce86ad3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019fecad-8bc0-76c3-a3ce-8f71f659ea5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fecad-8bc0-76c3-a3ce-8f71f659ea5b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fecad-8bc0-76c3-a3ce-8f71f659ea5b" xlink:to="loc_us-gaap_SegmentDomain_019fecad-8bc0-76c3-a3ce-8f71f659ea5b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019fecad-8bc0-786e-87e1-1d14069ad4fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019fecad-8bc0-76c3-a3ce-8f71f659ea5b" xlink:to="loc_us-gaap_SegmentDomain_019fecad-8bc0-786e-87e1-1d14069ad4fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_EPSegmentMember_019fecad-8bc0-729b-903e-d06aba43f14a" xlink:href="sm-20260930.xsd#sm_EPSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019fecad-8bc0-786e-87e1-1d14069ad4fb" xlink:to="loc_sm_EPSegmentMember_019fecad-8bc0-729b-903e-d06aba43f14a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NatureOfExpenseAxis_019fecad-8bc0-77a8-83b7-c7ca050fc062" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NatureOfExpenseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019fecad-8bc0-74c7-a99a-f11e1ce86ad3" xlink:to="loc_us-gaap_NatureOfExpenseAxis_019fecad-8bc0-77a8-83b7-c7ca050fc062" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77a8-83b7-c7ca050fc062_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterimPeriodCostsNotAllocableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NatureOfExpenseAxis_019fecad-8bc0-77a8-83b7-c7ca050fc062" xlink:to="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77a8-83b7-c7ca050fc062_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterimPeriodCostsNotAllocableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NatureOfExpenseAxis_019fecad-8bc0-77a8-83b7-c7ca050fc062" xlink:to="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_LeaseOperatingExpenseMember_019fecad-8bc0-7154-b150-1c888dd12dfe" xlink:href="sm-20260930.xsd#sm_LeaseOperatingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:to="loc_sm_LeaseOperatingExpenseMember_019fecad-8bc0-7154-b150-1c888dd12dfe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_TransportationCostsMember_019fecad-8bc0-782c-83b1-6d2643d9b2d5" xlink:href="sm-20260930.xsd#sm_TransportationCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:to="loc_sm_TransportationCostsMember_019fecad-8bc0-782c-83b1-6d2643d9b2d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_ProductionTaxesMember_019fecad-8bc0-7934-9a6b-4c454430f336" xlink:href="sm-20260930.xsd#sm_ProductionTaxesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:to="loc_sm_ProductionTaxesMember_019fecad-8bc0-7934-9a6b-4c454430f336" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_AdValoremTaxMember_019fecad-8bc0-7fc8-baba-72b4eca01274" xlink:href="sm-20260930.xsd#sm_AdValoremTaxMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterimPeriodCostsNotAllocableDomain_019fecad-8bc0-77b9-9b1b-4bb825ff033b" xlink:to="loc_sm_AdValoremTaxMember_019fecad-8bc0-7fc8-baba-72b4eca01274" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019fecad-8bc0-792e-9eca-49eea4742d5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_Revenues_019fecad-8bc0-792e-9eca-49eea4742d5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_019fecad-8bc0-73cd-9971-7d172c77f5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization_019fecad-8bc0-73cd-9971-7d172c77f5a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResultsOfOperationsDepreciationDepletionAmortizationAndAccretion_019fecad-8bc0-767b-bb42-9c2e79a6e0ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResultsOfOperationsDepreciationDepletionAmortizationAndAccretion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_ResultsOfOperationsDepreciationDepletionAmortizationAndAccretion_019fecad-8bc0-767b-bb42-9c2e79a6e0ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExplorationExpense_019fecad-8bc0-74a2-8ea8-404e6170f993" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExplorationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_ExplorationExpense_019fecad-8bc0-74a2-8ea8-404e6170f993" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019fecad-8bc0-70f3-a8a7-2df1fec0e205" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019fecad-8bc0-70f3-a8a7-2df1fec0e205" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019fecad-8bc0-7692-9041-00e50e41c578" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_GainLossOnDerivativeInstrumentsNetPretax_019fecad-8bc0-7692-9041-00e50e41c578" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseNet_019fecad-8bc0-71d6-999d-1b939d076896" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherOperatingIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseNet_019fecad-8bc0-71d6-999d-1b939d076896" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019fecad-8bc0-7401-a79f-1d93eb615b50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_InterestExpense_019fecad-8bc0-7401-a79f-1d93eb615b50" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndOtherIncome_019fecad-8bc0-729a-b2e9-b9cba208c06d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestAndOtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_InterestAndOtherIncome_019fecad-8bc0-729a-b2e9-b9cba208c06d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019fecad-8bc0-7fcf-925b-eafaf4069d03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019fecad-8bc0-7fcf-925b-eafaf4069d03" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019fecad-8bc0-73ad-9389-30da150def16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019fecad-8bc0-73ad-9389-30da150def16" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019fecad-8bc0-732b-b63f-16b915dd816b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019fecad-8bc0-79f7-9720-356eeb4d4d92" xlink:to="loc_us-gaap_NetIncomeLoss_019fecad-8bc0-732b-b63f-16b915dd816b" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://sm-energy.com/role/StockBasedCompensationDetails" xlink:type="simple" xlink:href="sm-20260930.xsd#StockBasedCompensationDetails"/>
  <link:definitionLink xlink:role="http://sm-energy.com/role/StockBasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fecad-8bc0-7662-83b0-689e695b7607" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fecad-8bc0-7662-83b0-689e695b7607" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019fecad-8bc0-7c04-a4f0-91494a594fe6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fecad-8bc0-7662-83b0-689e695b7607" xlink:to="loc_us-gaap_AwardTypeAxis_019fecad-8bc0-7c04-a4f0-91494a594fe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fecad-8bc0-7c04-a4f0-91494a594fe6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019fecad-8bc0-7c04-a4f0-91494a594fe6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fecad-8bc0-7c04-a4f0-91494a594fe6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fecad-8bc0-725d-b455-d2db3c3767c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019fecad-8bc0-7c04-a4f0-91494a594fe6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fecad-8bc0-725d-b455-d2db3c3767c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019fecad-8bc0-7f2a-bec8-956e3a413325" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fecad-8bc0-725d-b455-d2db3c3767c7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019fecad-8bc0-7f2a-bec8-956e3a413325" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fecad-8bc0-7662-83b0-689e695b7607" xlink:to="loc_us-gaap_PlanNameAxis_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd" xlink:to="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7b00-9707-787f8821595d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019fecad-8bc0-7ca1-ae08-3ec2e2bbd0fd" xlink:to="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7b00-9707-787f8821595d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A2025SMEquityIncentiveCompensationPlanMember_019fecad-8bc0-74a3-899e-2af37534f306" xlink:href="sm-20260930.xsd#sm_A2025SMEquityIncentiveCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7b00-9707-787f8821595d" xlink:to="loc_sm_A2025SMEquityIncentiveCompensationPlanMember_019fecad-8bc0-74a3-899e-2af37534f306" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_A2024CivitasLongTermIncentivePlanMember_019fecad-8bc0-74e6-af51-55753253f3f2" xlink:href="sm-20260930.xsd#sm_A2024CivitasLongTermIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019fecad-8bc0-7b00-9707-787f8821595d" xlink:to="loc_sm_A2024CivitasLongTermIncentivePlanMember_019fecad-8bc0-74e6-af51-55753253f3f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7459-b3b0-f83595eae690" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019fecad-8bc0-7662-83b0-689e695b7607" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7459-b3b0-f83595eae690" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7459-b3b0-f83595eae690_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7459-b3b0-f83595eae690" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7459-b3b0-f83595eae690_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7779-b8df-f87f032e2003" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019fecad-8bc0-7459-b3b0-f83595eae690" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7779-b8df-f87f032e2003" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-744c-a7a6-cb2496f5a908" xlink:href="sm-20260930.xsd#sm_CivitasResourcesMergerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019fecad-8bc0-7779-b8df-f87f032e2003" xlink:to="loc_sm_CivitasResourcesMergerMember_019fecad-8bc0-744c-a7a6-cb2496f5a908" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019fecad-8bc0-7be3-939f-e3a97ba5e319" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019fecad-8bc0-7be3-939f-e3a97ba5e319" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019fecad-8bc0-7704-9b81-e59a3e65361c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019fecad-8bc0-7704-9b81-e59a3e65361c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_sm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue_019fecad-8bc0-77c7-af05-e0b570e338aa" xlink:href="sm-20260930.xsd#sm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:to="loc_sm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodGrantDateFairValue_019fecad-8bc0-77c7-af05-e0b570e338aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019fecad-8bc0-7620-beeb-c11db322234f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019fecad-8bc0-7961-8298-7f5796d05f1b" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019fecad-8bc0-7620-beeb-c11db322234f" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
