It's official! No one has to wonder anymore if Justin Bieber and Hailey Baldwin are hooking up, because Justin's new Instagram of the two kissing sure seems to confirm it!

If you thought Justin might be hooking up with Kourtney Kardashian or some random Adidas model -- well, you're probably right -- but that doesn't mean he's not hooking up with his "friend" Hailey Baldwin, too!

Justin posted this Instagram of him and Hailey kissing on New Year's Eve AND they were already posting cozy pix from Anguilla AND they both went to Leonardo DiCaprio's NYE party in St. Barth AND they've been pretty close for quite while ... which usually means ... friends with benefits!