Justin Bieber's having a hard time keeping his shirt on ... and the struggle is real.
The Biebs went mostly shirtless over the weekend in WeHo as he hit up a skate park. The "Purpose" singer has a pretty good reason for going skins -- just look at that bod. Need we say more?
The shirt did serve one good purpose ... blocking those rays. Skateboarding is cool and all ... but for our money, we'll take reservations for 1 in Laguna Beach.