Lady Gaga Groped While Crowd Surfing!

Lady Gaga does not mind a hand or 2 -- or 10 -- on her ass when she's performing ... 'cause she let her fans do just that Thursday night.

Gaga was performing at The Satellite in L.A. Thursday wearing booty shorts, when she fell butt first into a full-on crowd surf. In their defense, concertgoers were just holding her up ... but her cheeks were fully up for grabs in the process.