Who's that girl?! We have no idea! But Leonardo DiCaprio definitely picked her up off the side of the road on Tuesday morning after partying the night away with Justin Bieber on Monday night. We didn't the two were friends but it looks like JB is the newest member of Leo's infamous "P*ssy Posse."

Driving his Mercedes-Benz, Leo picked up the mystery brunette after living it up at 1Oak with Justin Bieber the night before. The babe was decked out in all black and got into the back seat, as Leo's bud was in the passenger seat.

Does anyone see a casual double team in this chick's future?