SMH! NATE DOGG SEX TAPE BEING SHOPPED!

A 5-minute sex tape featuring the late Nate Dogg and an unidentified female lover has surfaced ... and it's being shopped to various media outlets.

TMZ has seen the tape -- shot several years ago -- and it's pretty much what you'd expect ... a lot of sex ... two different positions ... and a sexy Luther Vandross soundtrack.

Sources say ... the person in possession of the tape is currently shopping it around to the usual porn studios. So far, no takers.

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