He's one of the hottest acts on Earth ... so Bruno Mars could make just about any backstage demand he wants -- exotic foods, imported candy, baby pandas -- but turns out his one must-have item is ... a clean ass!
We caught up with Bruno in the Valley (he's so not a Valley guy) ... and asked him about crazy riders ... aka the dressing room luxuries musicians demand while on the road.
Van Halen famously banned brown M&Ms ... Lady Gaga wants a nude mannequin, and Marilyn Manson ... a hairless hooker, naturally.
But Bruno told us he keeps it simple -- WET WIPES!
Watch the video ... there is one other thing he needs to accompany the wipes -- but you gotta admire a superstar who puts hygiene first.