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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-08-11</periodOfReport>

    <issuer>
        <issuerCik>0000101594</issuerCik>
        <issuerName>US ENERGY CORP</issuerName>
        <issuerTradingSymbol>USEG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001065880</rptOwnerCik>
            <rptOwnerName>FRASER H RUSSELL</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>877 N 8TH ST W</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>RIVERTON</rptOwnerCity>
            <rptOwnerState>WY</rptOwnerState>
            <rptOwnerZipCode>82501</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-08-11</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4050</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.02</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21363</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1300</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.25</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2002-08-08</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-12-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.4</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-01-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.46</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-07-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>50000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>50000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.88</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>1998-12-04</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-09-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>12500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12500</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.86</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-10-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-10-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.9</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-12-07</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-12-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F5">Options issued to Reporting Person as a member of the Issuer's Board of Directors.</footnote>
        <footnote id="F1">Includes 1,000 shares held in joint tenancy with the Reporting Person's wife.</footnote>
        <footnote id="F3">Includes 4,000 shares held in an Individual Retirement Account (IRA) for the benefit of the Reporting Person.</footnote>
        <footnote id="F2">Includes shares directly owned by the reporting person.</footnote>
        <footnote id="F4">Includes 1,300 shares held in an IRA established for the benefit of the Reporting Person's wife. The Reporting Person disclaims any beneficial interest in these shares.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robert Scott Lorimer - Attorney in Fact</signatureName>
        <signatureDate>2008-08-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2008-08-11
0000101594
US ENERGY CORP
USEG
0001065880
FRASER H RUSSELL
877 N 8TH ST W
RIVERTON
WY
82501
1
0
0
0
Common Stock
2008-08-11
4
D
0
4050
3.02
D
21363
D
Common Stock
1300
I
By Spouse
Stock Options (Right to buy)
2.25
2002-08-08
2011-12-06
Common Stock
10000
10000
D
Stock Options (Right to buy)
2.4
2001-01-01
2011-01-09
Common Stock
10000
10000
D
Stock Options (Right to buy)
2.46
2005-07-01
2014-06-30
Common Stock
50000
50000
D
Stock Options (Right to buy)
2.88
1998-12-04
2008-09-24
Common Stock
12500
12500
D
Stock Options (Right to buy)
3.86
2005-10-14
2015-10-13
Common Stock
25000
25000
D
Stock Options (Right to buy)
3.9
2001-12-07
2011-12-07
Common Stock
20000
20000
D
Options issued to Reporting Person as a member of the Issuer's Board of Directors.
Includes 1,000 shares held in joint tenancy with the Reporting Person's wife.
Includes 4,000 shares held in an Individual Retirement Account (IRA) for the benefit of the Reporting Person.
Includes shares directly owned by the reporting person.
Includes 1,300 shares held in an IRA established for the benefit of the Reporting Person's wife. The Reporting Person disclaims any beneficial interest in these shares.
Robert Scott Lorimer - Attorney in Fact
2008-08-13