R&B singer Bobby valentino's sex tape leaked

"Sex in the Lounge" singer Bobby V doesn't limit himself to lounges ... he does the nasty in all kinds of rooms ... as evidenced by a new sex tape claiming to feature the R&B singer being shopped to the highest bidder.

The XXX vid -- which we've seen -- is several glorious minutes of Bobby doing his best impersonation of Ray J ... i.e. getting it on inside a hotel room while filming himself at the same time.

Specifically, Bobby and the naked chick -- who we're told is a video vixen -- kick things off with some very specific touching ... before diving in to the full on sex-having.

The seller is clearly looking to make a buck off the sale and it's unclear if Bobby is aware the steamy vid is being shopped.