Bieber -- fresh off the jet from Bora Bora -- was strolling with Hailey Baldwin on Wednesday when they bumped into Wahlberg. Mark gave Justin a few attaboy taps on the shoulder during their brief chat, but we have no clue what they bro'd down about.
Of course, they both famously modeled Calvins -- 20-something years apart. We'd like to imagine JB said something all Star Wars-y like, "Now I am the master!"
But we know that didn't happen ... 'cause Wahlberg woulda knocked him out.