When Chris Brown sings, the panties start dropping ... and TMZ has the footage to prove it.
Chris was performing at Heat Nightclub in Anaheim Saturday ... when a very generous female fan handed the singer a silky white thong as a present.
Unclear, from the footage, if it was used or not -- but witnesses on scene tell us the club was super hot and sweaty, sooooo ...
Watch Chris' reaction to the gifted panty -- he's definitely NOT a germaphobe.
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