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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-04-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001065872</rptOwnerCik>
            <rptOwnerName>LARSEN KEITH G</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>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CHAIRMAN &amp; CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-04-01</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2008-04-05</value>
            </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>3.1</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>254335</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>65853</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>120700</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Immediate Family</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>155811</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</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>2011-12-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>52556</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52556</value>
                    <footnoteId id="F6"/>
                </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>2001-01-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>267734</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>267734</value>
                    <footnoteId id="F7"/>
                </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>2004-07-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>59350</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>59350</value>
                    <footnoteId id="F6"/>
                </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>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                    <footnoteId id="F6"/>
                </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>2011-12-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                    <footnoteId id="F6"/>
                </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>150000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>150000</value>
                    <footnoteId id="F8"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <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="F6">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="F7">Includes stock options granted under the Issuer's 1998 Incentive Stock Option Plan and exempt under Rule 16b-3.</footnote>
        <footnote id="F8">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>
        <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 second 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="F5">Shares issued to be held in the ESOP which are not allocated to accounts established for the benefit of specific plan participants.  The Reporting Person, as an ESOP Trustee, exercises the voting powers with respect to such unallocated shares.</footnote>
        <footnote id="F4">Includes a balance of shares held in ESOP accounts established to benefit members of the Reporting Persons 'Immediate Family' as that term is defined in Rule 16a-1(e) in accordance with Rule 16a-8(b)(2).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>KEITHG.LARSEN</signatureName>
        <signatureDate>2008-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2008-04-01
0000101594
US ENERGY CORP
USEG
0001065872
LARSEN KEITH G
877 N 8TH ST W
RIVERTON
WY
82501
1
1
0
0
CHAIRMAN & CEO
Common Stock
2008-04-01
2008-04-05
4
J
0
5000
3.1
A
254335
D
Common Stock
65853
I
By ESOP
Common Stock
120700
I
By Immediate Family
Common Stock
155811
I
By Trust
Stock Options (Right to buy)
2.25
2002-08-08
2011-12-07
Common Stock
52556
52556
D
Stock Options (Right to buy)
2.4
2001-01-10
2011-01-09
Common Stock
267734
267734
D
Stock Options (Right to buy)
2.46
2004-07-01
2014-06-30
Common Stock
59350
59350
D
Stock Options (Right to buy)
3.86
2005-10-14
2015-10-13
Common Stock
100000
100000
D
Stock Options (Right to buy)
3.9
2001-12-07
2011-12-06
Common Stock
100000
100000
D
Stock Options (Right to buy)
4.97
2008-01-01
2017-07-26
Common Stock
150000
150000
D
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.
Includes stock options granted under the Issuer's 1998 Incentive Stock Option Plan and exempt under Rule 16b-3.
Stock options granted under the Issuer's 2001 Incentive Stock Option Plan with a 5 year vesting schedule and exempt under Rule 16b-3.
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 second 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.
Shares issued to be held in the ESOP which are not allocated to accounts established for the benefit of specific plan participants.  The Reporting Person, as an ESOP Trustee, exercises the voting powers with respect to such unallocated shares.
Includes a balance of shares held in ESOP accounts established to benefit members of the Reporting Persons 'Immediate Family' as that term is defined in Rule 16a-1(e) in accordance with Rule 16a-8(b)(2).
KEITHG.LARSEN
2008-04-02