It's NOT KOURTNEY, people!!!

All these websites are reporting it's Kourtney Kardashian straddling Justin Bieber on a matte black Audi yesterday have got it TOTALLY WRONG! Seriously? Everyone things that long skinny leg is Kourtney? And everyone really believes Kourtney and Justin are hooking up?

Well let's just say Bieber sewing is his wild oats with plenty of other girls -- he doesn't need to steal Scott Disick's lady.

We spotted Beiber in Newport Beach yesterday having a grand ol' time with a hot blonde and lots of friends. And did they just pose for the Instagram he posted and call it a day? No, bitches -- they chartered a yacht and partied into the night! Beiber knows how to do it, y'all. He's not new at this. Lord knows ...