Chris Brown is celebrating his birthday without Rihanna ... and with Karrueche Tran. We bet this will end well!

Breezy, who turns 24 today (May 5), celebrated on Friday night (May 3) in New York City with Tran by his side. Us Weekly reports that Tran rolled up to the Emerson Theatre with Brown and his entourage, sitting side by side with the 'Fine China' singer. But that doesn't mean she was having a good time.

"She didn't look very happy," a witness told the tab. "He didn't appear to be paying much attention to her and was partying around a lot of girls." Ouch! The source added that Tran left the group a little while later.

While RiRi likely won't be thrilled by the news, she also doesn't have much time to devote to her tumultuous relationship with Brown. A source said, "This tour is her life right now." Still, she did give Brown a Benz for his b-day, so it's clear there's still something up. As for Brown, he's previously said he had a hard time leaving Tran behind -- even after she met Rihanna -- so hopefully they find some sort of solution to this. Real love isn't this complicated!

Watch the Chris Brown 'Fine China' Video