Celebrity Butts -- Guess the Summer Bum!

Can you guess which Hollywood hottie put her summer booty on full display in this eye-popping hot shot?!

"BeyondBeautyStar" was her first YouTube name ... She covers topics like beauty routines, traveling, and workouts ... and scored a hosting gig for the "Teen Vogue" channel. Needless to say, Finneas is one lucky man!