Justin Bieber BALLIN' OUT WITH NEYMAR

Bend it like ... Bieber?!?

Justin Bieber put on his electric green cleats and hit the pitch with Neymar at FC Barcelona's training facility ... and wound up in a penalty shootout with one of the best players in the world.

Watch the clip ... Bieber strikes pretty well -- and actually scores a few shots on Rafinha -- a midfielder for the Spanish club.

Bieber also put on a show with his dribbling skills before posing for a pic with Lionel Messi.

So, if all of these mega rich dudes go out for drinks ... who pays??