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

    <documentType>4</documentType>
    <periodOfReport>2003-12-12</periodOfReport>
    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000101778</issuerCik>
        <issuerName>MARATHON OIL CORP</issuerName>
        <issuerTradingSymbol>MRO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001271651</rptOwnerCik>
            <rptOwnerName>KAPLAN ALARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MARATHON OIL CORPORATION</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>V.P. - Major Projects</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>
  <nonDerivativeTable>
  </nonDerivativeTable>
  <derivativeTable>
   <derivativeTransaction>
      <securityTitle>
          <value>Employee Stock Option (Right to Buy)</value>
      </securityTitle>
      <conversionOrExercisePrice>
          <value>30.875</value>
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2003-12-12</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F1" />
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>15000.00</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
              <footnoteId id="F2" />
      </exerciseDate>
      <expirationDate>
          <value>2013-12-12</value>
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>COMMON STOCK</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>15000.00</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>15000.00</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
   <derivativeTransaction>
      <securityTitle>
          <value>Stock Appreciation Right</value>
      </securityTitle>
      <conversionOrExercisePrice>
          <value>30.875</value>
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2003-12-12</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F1" />
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>15000.00</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
              <footnoteId id="F2" />
      </exerciseDate>
      <expirationDate>
          <value>2013-12-12</value>
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>COMMON STOCK</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>15000.00</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>15000.00</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
  </derivativeTable>
<footnotes>
   <footnote id="F1">The employee stock option and stock appreciation right granted in tandem under the Marathon Oil Corporation 2003 Incentive Compen
sation Plan.  Accordingly, the exercise of one results in the cancellation of the other.</footnote>
   <footnote id="F2">Vests in three equal annual installments on December 12, 2004, 2005, and 2006.</footnote>
</footnotes>
<remarks></remarks>    <ownerSignature>
       <signatureName>By: R.J. Kolencik, Attorney-in-Fact for Alard Kaplan</signatureName>
       <signatureDate>2003-12-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0201
4
2003-12-12
0
0000101778
MARATHON OIL CORP
MRO
0001271651
KAPLAN ALARD
C/O MARATHON OIL CORPORATION
5555 SAN FELIPE ROAD
HOUSTON
TX
77056
0
1
0
0
V.P. - Major Projects
Employee Stock Option (Right to Buy)
30.875
2003-12-12
4
A
0
15000.00
0
A
2013-12-12
COMMON STOCK
15000.00
15000.00
D
Stock Appreciation Right
30.875
2003-12-12
4
A
0
15000.00
0
A
2013-12-12
COMMON STOCK
15000.00
15000.00
D
The employee stock option and stock appreciation right granted in tandem under the Marathon Oil Corporation 2003 Incentive Compen
sation Plan.  Accordingly, the exercise of one results in the cancellation of the other.
Vests in three equal annual installments on December 12, 2004, 2005, and 2006.
By: R.J. Kolencik, Attorney-in-Fact for Alard Kaplan
2003-12-15