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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-07-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001332609</rptOwnerCik>
            <rptOwnerName>YOUNGBAUER STEVEN R</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>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SECRETARY &amp; GENERAL COUNSEL</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-07-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.11</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>71574</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13575</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.46</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-07-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                    <footnoteId id="F4"/>
                </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>50000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>50000</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.97</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-01-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2017-07-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares issued to the Reporting Person under the USEG 2001 Stock Compensation Plan. The issuance of these shares is for the funding obligation under the plan for the third quarter of the calendar year ending December 31, 2008. The Issuer has agreed under the terms of the Plan to pay all taxes due. The Reporting Person has agreed not to sell these shares to the market or pledge them on obligations until after his (i) retirement; (ii) total disability or (iii) in the case of the death of the Reporting Person his estate may sell the shares of stock.</footnote>
        <footnote id="F3">Includes shares held in the U.S. Energy Corp. Employee Stock Ownership Plan (the'ESOP') in an account established for the benefit of the Reporting Person.</footnote>
        <footnote id="F4">Includes stock options granted under the Issuer's 2001 Incentive Stock Option Plan and exempt under Rule 16b-3.</footnote>
        <footnote id="F2">Includes shares held directly by the Reporting Person.</footnote>
        <footnote id="F5">Stock options granted under the Issuer's 2001 Incentive Stock Option Plan with a 5 year vesting schedule and exempt under Rule 16b-3.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>STEVENR.YOUNGBAUER</signatureName>
        <signatureDate>2008-07-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2008-07-01
0000101594
US ENERGY CORP
USEG
0001332609
YOUNGBAUER STEVEN R
877 N 8TH ST W
RIVERTON
WY
82501
0
1
0
0
SECRETARY & GENERAL COUNSEL
Common Stock
2008-07-01
4
J
0
5000
3.11
A
71574
D
Common Stock
13575
I
By ESOP
Stock Options (Right to buy)
2.46
2004-07-01
2014-06-30
Common Stock
25000
25000
D
Stock Options (Right to buy)
3.86
2005-10-14
2015-10-13
Common Stock
50000
50000
D
Stock Options (Right to buy)
4.97
2008-01-01
2017-07-26
Common Stock
100000
100000
D
Shares issued to the Reporting Person under the USEG 2001 Stock Compensation Plan. The issuance of these shares is for the funding obligation under the plan for the third quarter of the calendar year ending December 31, 2008. The Issuer has agreed under the terms of the Plan to pay all taxes due. The Reporting Person has agreed not to sell these shares to the market or pledge them on obligations until after his (i) retirement; (ii) total disability or (iii) in the case of the death of the Reporting Person his estate may sell the shares of stock.
Includes shares held in the U.S. Energy Corp. Employee Stock Ownership Plan (the'ESOP') in an account established for the benefit of the Reporting Person.
Includes stock options granted under the Issuer's 2001 Incentive Stock Option Plan and exempt under Rule 16b-3.
Includes shares held directly by the Reporting Person.
Stock options granted under the Issuer's 2001 Incentive Stock Option Plan with a 5 year vesting schedule and exempt under Rule 16b-3.
STEVENR.YOUNGBAUER
2008-07-01