<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
    <periodOfReport>2003-08-22</periodOfReport>
    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000101778</issuerCik>
        <issuerName>MARATHON OIL CORP</issuerName>
        <issuerTradingSymbol>MRO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001238370</rptOwnerCik>
            <rptOwnerName>GOLDER G DAVID</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>MARATHON OIL CORP</rptOwnerStreet1>
            <rptOwnerStreet2>5555 SAN FELIPE ROAD</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77056</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. V. P.-Commercial. and Dev.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>
  <nonDerivativeTable>
   <nonDerivativeTransaction>
      <securityTitle>
          <value>COMMON STOCK</value>
      </securityTitle>
      <transactionDate>
          <value>2003-08-22</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>I</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F1" />
      </transactionCoding>
      <transactionTimeliness>
      <value />
      </transactionTimeliness>
      <transactionAmounts>
          <transactionShares>
              <value>3590.509</value>
              <footnoteId id="F2" />
          </transactionShares>
          <transactionPricePerShare>
              <value>27.13</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>D</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>27332.000</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </nonDerivativeTransaction>
  </nonDerivativeTable>
  <derivativeTable>
   <derivativeTransaction>
      <securityTitle>
          <value>Phantom Stock</value>
      </securityTitle>
      <conversionOrExercisePrice>
              <footnoteId id="F3" />
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2003-08-22</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>I</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F4" />
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>1161.166</value>
              <footnoteId id="F5" />
          </transactionShares>
          <transactionPricePerShare>
              <value>26.82</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>D</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
              <footnoteId id="F6" />
      </exerciseDate>
      <expirationDate>
              <footnoteId id="F7" />
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>COMMON STOCK</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>1161.166</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>0.000</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
  </derivativeTable>
<footnotes>
   <footnote id="F1">Transfer out of issuer stock fund into another fund in Marathon Oil CompanyThrift Plan.</footnote>
   <footnote id="F2">Includes 31.058 shares, previously not reported, allocated to issuer stock fund for reporting person's account in Marathon Oil Co
mpany Thrift Plan. </footnote>
   <footnote id="F3">1-for-1</footnote>
   <footnote id="F4">Transfer out of issuer phantom stock fund into another fund in Marthon Oil Company Deferred Compensation Plan. </footnote>
   <footnote id="F5">Includes dividends of 21.24 shares at average weighted price of 24.81 per share, previously not reported pursuant to Rule 16a-11,
 for reporting person's phantom stock account in Marathon Oil Company Deferred Compensation Plan.</footnote>
   <footnote id="F6">Immediately</footnote>
   <footnote id="F7">Shares of Phantom Stock are payable in cash following the termination of the reporting person's employment.</footnote>
</footnotes>
    <ownerSignature>
       <signatureName>By: Richard J. Kolencik, Attorney-in-Fact for G. David Golde</signatureName>
       <signatureDate>2003-08-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "doc4.xml", "description": "PRIMARY DOCUMENT", "secsgml_size_bytes": 5686}]
X0201
4
2003-08-22
0
0000101778
MARATHON OIL CORP
MRO
0001238370
GOLDER G DAVID
MARATHON OIL CORP
5555 SAN FELIPE ROAD
HOUSTON
TX
77056
0
1
0
0
Sr. V. P.-Commercial. and Dev.
COMMON STOCK
2003-08-22
4
I
0
3590.509
27.13
D
27332.000
D
Phantom Stock
2003-08-22
4
I
0
1161.166
26.82
D
COMMON STOCK
1161.166
0.000
D
Transfer out of issuer stock fund into another fund in Marathon Oil CompanyThrift Plan.
Includes 31.058 shares, previously not reported, allocated to issuer stock fund for reporting person's account in Marathon Oil Co
mpany Thrift Plan.
1-for-1
Transfer out of issuer phantom stock fund into another fund in Marthon Oil Company Deferred Compensation Plan.
Includes dividends of 21.24 shares at average weighted price of 24.81 per share, previously not reported pursuant to Rule 16a-11,
 for reporting person's phantom stock account in Marathon Oil Company Deferred Compensation Plan.
Immediately
Shares of Phantom Stock are payable in cash following the termination of the reporting person's employment.
By: Richard J. Kolencik, Attorney-in-Fact for G. David Golde
2003-08-25