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

    <documentType>4</documentType>
    <periodOfReport>2004-01-16</periodOfReport>
    <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000101778</issuerCik>
        <issuerName>MARATHON OIL CORP</issuerName>
        <issuerTradingSymbol>MRO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001216484</rptOwnerCik>
            <rptOwnerName>CLARK JANET F</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>Sr. V.P. and CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>
  <nonDerivativeTable>
   <nonDerivativeTransaction>
      <securityTitle>
          <value>COMMON STOCK</value>
      </securityTitle>
      <transactionDate>
          <value>2004-01-16</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F1" />
      </transactionCoding>
      <transactionTimeliness>
      <value />
      </transactionTimeliness>
      <transactionAmounts>
          <transactionShares>
              <value>15000.000</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>15000.000</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </nonDerivativeTransaction>
  </nonDerivativeTable>
  <derivativeTable>
   <derivativeTransaction>
      <securityTitle>
          <value>Employee Stock Option (Right to Buy)</value>
      </securityTitle>
      <conversionOrExercisePrice>
          <value>33.415</value>
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2004-01-16</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F2" />
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>20000.00</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
          <value>2005-01-16</value>
              <footnoteId id="F3" />
      </exerciseDate>
      <expirationDate>
          <value>2014-01-16</value>
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>COMMON STOCK</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>20000.00</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>20000.00</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
   <derivativeTransaction>
      <securityTitle>
          <value>Stock Appreciation Right</value>
      </securityTitle>
      <conversionOrExercisePrice>
          <value>33.415</value>
      </conversionOrExercisePrice>
      <transactionDate>
          <value>2004-01-16</value>
      </transactionDate>
      <transactionCoding>
          <transactionFormType>4</transactionFormType>
          <transactionCode>A</transactionCode>
          <equitySwapInvolved>0</equitySwapInvolved>
              <footnoteId id="F2" />
      </transactionCoding>
      <transactionAmounts>
          <transactionShares>
              <value>20000.00</value>
          </transactionShares>
          <transactionPricePerShare>
              <value>0</value>
          </transactionPricePerShare>
          <transactionAcquiredDisposedCode>
              <value>A</value>
          </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
          <value>2005-01-16</value>
              <footnoteId id="F3" />
      </exerciseDate>
      <expirationDate>
          <value>2014-01-16</value>
      </expirationDate>
      <underlyingSecurity>
          <underlyingSecurityTitle>
              <value>COMMON STOCK</value>
          </underlyingSecurityTitle>
          <underlyingSecurityShares>
              <value>20000.00</value>
          </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
          <sharesOwnedFollowingTransaction>
              <value>20000.00</value>
          </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
          <directOrIndirectOwnership>
              <value>D</value>
          </directOrIndirectOwnership>
      </ownershipNature>
   </derivativeTransaction>
  </derivativeTable>
<footnotes>
   <footnote id="F1">Grant under the Marathon Oil Corporation 2003 Incentive Compensation Plan.</footnote>
   <footnote id="F2">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="F3">Vests in three cumulative annual installments of 6,666, 6,666, and 6,668 shares on January 16, 2005, 2006, and 2007, respectively
..</footnote>
</footnotes>
<remarks></remarks>    <ownerSignature>
       <signatureName>By:  R. J. Kolencik, Attorney-in-Fact for Janet F. Clark</signatureName>
       <signatureDate>2004-01-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "doc4.xml", "description": "PRIMARY DOCUMENT", "secsgml_size_bytes": 7055}]
X0201
4
2004-01-16
0
0000101778
MARATHON OIL CORP
MRO
0001216484
CLARK JANET F
C/O MARATHON OIL CORPORATION
5555 SAN FELIPE ROAD
HOUSTON
TX
77056
0
1
0
0
Sr. V.P. and CFO
COMMON STOCK
2004-01-16
4
A
0
15000.000
0
A
15000.000
D
Employee Stock Option (Right to Buy)
33.415
2004-01-16
4
A
0
20000.00
0
A
2005-01-16
2014-01-16
COMMON STOCK
20000.00
20000.00
D
Stock Appreciation Right
33.415
2004-01-16
4
A
0
20000.00
0
A
2005-01-16
2014-01-16
COMMON STOCK
20000.00
20000.00
D
Grant under the Marathon Oil Corporation 2003 Incentive Compensation Plan.
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 cumulative annual installments of 6,666, 6,666, and 6,668 shares on January 16, 2005, 2006, and 2007, respectively
..
By:  R. J. Kolencik, Attorney-in-Fact for Janet F. Clark
2004-01-20