<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-02-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000101778</issuerCik>
        <issuerName>MARATHON OIL CORP</issuerName>
        <issuerTradingSymbol>MRO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001238372</rptOwnerCik>
            <rptOwnerName>LOWDEN STEVEN J</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.-Bus. Dev./Int. Gas</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>COMMON STOCK</value>
            </securityTitle>
            <transactionDate>
                <value>2005-02-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>716.000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>32.52</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>35026.000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On February 4, 2005, the reporting person filed a Form 4 with the SEC reporting the exercise of stock appreciation rights on February 2, 2005, using the highest fair market value of Marathon Oil Corporation common stock during the period from February 1 thru February 2, 2005, which was $39.61.  The stock appreciation rights were subject to adjustment to reflect the highest fair market value during the ten day trading period commencing February 1, 2005.  This Form 4 reflects the number of shares the reporting person acquired based on the adjustment to reflect the highest fair market value of Marathon Oil Corporation common stock during such ten day trading period, which was $42.58.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By: R. J. Kolencik, Attorney-in-Fact for Steve J. Lowden</signatureName>
        <signatureDate>2005-02-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-02-14
0
0000101778
MARATHON OIL CORP
MRO
0001238372
LOWDEN STEVEN J
C/O MARATHON OIL CORPORATION
5555 SAN FELIPE ROAD
HOUSTON
TX
77056
0
1
0
0
Sr. V.P.-Bus. Dev./Int. Gas
COMMON STOCK
2005-02-14
4
J
0
716.000
32.52
A
35026.000
D
On February 4, 2005, the reporting person filed a Form 4 with the SEC reporting the exercise of stock appreciation rights on February 2, 2005, using the highest fair market value of Marathon Oil Corporation common stock during the period from February 1 thru February 2, 2005, which was $39.61.  The stock appreciation rights were subject to adjustment to reflect the highest fair market value during the ten day trading period commencing February 1, 2005.  This Form 4 reflects the number of shares the reporting person acquired based on the adjustment to reflect the highest fair market value of Marathon Oil Corporation common stock during such ten day trading period, which was $42.58.
By: R. J. Kolencik, Attorney-in-Fact for Steve J. Lowden
2005-02-15