Rihanna and ex Chris Brown ended up locked in the bathroom together at Meatpacking nightclub Griffin in the early hours of yesterday morning after dancing and making out on the dance floor. As celebs including Chris Rock and Dave Chappelle, former Giant Antonio Pierce and Tyson Beckford held court, Brown arrived with friends including rapper Bow Wow and sat at a table.

PHOTOS: RIHANNA

Five minutes later, Rihanna, who had been partying with pals at Catch, walked in with her friends. A source told us: “They sat two tables away from each other. Chris made his way over to Rihanna. He raised his shirt and was dancing promiscuously. Then they started dancing together and hugging and kissing in front of everyone.” Then, observers saw them go into the bathroom together, and when RiRi emerged, “She seemed a little ruffled” a source said. We’re told the pair, who broke up after Brown hit Rihanna during a fight before the 2009 Grammys, partied together until 4 a.m., when he left with his pals and she split five minutes later. A Griffin rep declined comment.