These sexy stars are making their way outdoors to to burn up the Hollywood scene by doing cool things like hiking, beaching and taking a dip in the pool ... the tops are coming off and the shirtless selfies are taking over social media.

See all the flexin' fellas ripping things up this season by flipping through our gallery of hot summer stomachs -- Get a really good look at the celebs showing off their six packs and pecks -- then see if you can guess which jacked star is responsible for the real heat.