The UFC superstar's cheeks make a brief cameo in the new Prime Video project that dropped on Thursday ... when at one point, Conor shows up wearing nothing but a smile on his face.

We're not going to reveal any spoilers -- the flick literally just dropped -- but considering Conor has talked about the nude scene in the promo tour leading up to the release, it's fair game to talk about the dude's peach.

It's pretty funny -- Conor previously stated he had no idea his "Knox" character would be shown in the buff ... but his dedication to the role kept him from turning down the opportunity to lay it all on the line.

Of course, "Road House" is a re-imagining of the 1989 cult classic ... and the late Patrick Swayze also shows off his tush in the original, too -- so apparently it's become quite the tradition for dudes to show skin in these flicks.

There's been a ton of hype around the Jake Gyllenhaal-led movie -- not only does Conor have a big role, but Post Malone also shows off his acting chops as well.