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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-08-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001238375</rptOwnerCik>
            <rptOwnerName>REINBOLT PAUL C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
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            <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., Finance and Treasurer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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            <transactionAmounts>
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                </transactionShares>
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                </transactionPricePerShare>
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                </transactionPricePerShare>
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                </transactionAcquiredDisposedCode>
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                </transactionPricePerShare>
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        <nonDerivativeTransaction>
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            </securityTitle>
            <transactionDate>
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                </transactionPricePerShare>
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    <derivativeTable>
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            </conversionOrExercisePrice>
            <transactionDate>
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            </transactionDate>
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            <transactionAmounts>
                <transactionShares>
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                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>1999-05-26</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-05-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>COMMON STOCK</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1300.000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>0.000</value>
                </sharesOwnedFollowingTransaction>
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            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-08-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
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            <transactionAmounts>
                <transactionShares>
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                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
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            </exerciseDate>
            <expirationDate>
                <value>2012-05-28</value>
            </expirationDate>
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                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
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            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>24500.000</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
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                    <value>24500.000</value>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Exercise of stock option and cancellation of tandem stock appreciation right.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By: R. J. Kolencik, Attorney-in-Fact for Paul C. Reinbolt</signatureName>
        <signatureDate>2005-08-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-08-23
0
0000101778
MARATHON OIL CORP
MRO
0001238375
REINBOLT PAUL C
C/O MARATHON OIL CORPORATION
5555 SAN FELIPE ROAD
HOUSTON
TX
77056
0
1
0
0
V.P., Finance and Treasurer
COMMON STOCK
2005-08-23
4
M
0
1300.000
34.00
A
19053.194
D
COMMON STOCK
2005-08-23
4
M
0
8000.000
28.12
A
27053.194
D
COMMON STOCK
2005-08-23
4
S
0
2200.000
59.74
D
24853.194
D
COMMON STOCK
2005-08-23
4
S
0
600.000
59.76
D
24253.194
D
COMMON STOCK
2005-08-23
4
S
0
6500.000
59.70
D
17753.194
D
EMPLOYEE STOCK OPTION (Right to Buy)
34.00
2005-08-23
4
M
0
1300.000
0
D
1999-05-26
2008-05-26
COMMON STOCK
1300.000
0.000
D
EMPLOYEE STOCK OPTION (Right to Buy)
28.12
2005-08-23
4
M
0
8000.000
0
D
2003-05-28
2012-05-28
COMMON STOCK
8000.000
24500.000
D
STOCK APPRECIATION RIGHT
28.12
2005-08-23
4
M
0
8000.000
0
D
2003-05-28
2012-05-28
COMMON STOCK
8000.000
24500.000
D
Exercise of stock option and cancellation of tandem stock appreciation right.
By: R. J. Kolencik, Attorney-in-Fact for Paul C. Reinbolt
2005-08-25