Justin Bieber's Taking Acting Lessons with Famous Coach

Justin Bieber's going hard into the acting world, working with a professional who's helped some of the biggest names in Hollywood -- but don't count on seeing his skills on a screen anytime soon.

Sources close to the Biebs tell TMZ ... he's taking acting lessons for the fun of it. We're told he's NOT working on any kind of project, he simply wanted to try acting lessons. Up til now, his resume consists of getting gunned down on 'CSI' and playing himself in "Zoolander 2."

Even though he says he's just goofing around, Justin's learning at Nancy Banks' studio in L.A. -- the same place celebs like Emma Stone, Rachel McAdams, Channing Tatum, Zac Efron, Forest Whitaker and many more hone their craft.

First a Grammy ... Emmy, Oscar and Tony next?