Bruno Mars Someone Better Have My ... WET WIPES!!

EXCLUSIVE

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.