Usher Flashes Bare Butt Onstage in Viral Moment From Chris Brown Tour

Usher's serving up some hot cakes during his tour with fellow R&B star Chris Brown ... exposing his bare butt to fans during a sensual number ... and it's on video.

The pop star is currently touring the country with Breezy ... and during a recent performance in Maryland, he stood up from a bed on stage and exposed his buck naked bottom.

Usher flashed some serious booty while performing "Seduction" ... he was simulating sex with a woman and he got out of bed while buttoning his pants.

After flashing his cheeks to the audience, Usher grabs a bar and starts doing some pullups.

Of course, Usher isn't the only performer getting naughty during these shows ... Chris has been grinding on some ladies from the audience. In fact, during this same tour stop he thrusted into a woman with her legs held high into the air.

And during his live show in Minneapolis, Breezy went to town on another woman while she was on all fours on a mattress on stage for a rendition of "Take You Down."