Chris Brown, Rihanna and Drake Credit: Debra L Rothenberg/Getty Images; Frazer Harrison/Getty Images; unday Times/Gallo Images/Getty Images

Now, now, boys -- don't fight!

Chris Brown sustained a bloody gash on his chin, sharing the pic on Twitter, following a nasty brawl with Drake and his posse in NYC early Thursday -- and Rihanna may have been the topic at issue.

NYPD confirmed to TMZ that Brown, 23, and Drake, 25 -- plus their respective entourages -- had a brutal fight at WIP nightclub in downtown Manhattan. Punches and bottles were thrown during the melee, in which five people sustained minor injuries.

Website Global Grind reports that Brown initially sent over a bottle to Drake's table; Drake then confronted Brown, punched him in the face and threw a bottle at him.

In an expletive-laden tweet that accompanied the photo of the cut on his chin, Brown wrote: "How u party wit rich n**** that hate? Lol... Throwing bottles like girls? #shameonya!."

Speculation abounds online that the R&B/hip-hop stars first exchanged words over singer Rihanna. The "We Found Love" singer has been secretly hooking up with ex-beau Brown for the past year and has been romantically linked to Drake (real name: Aubrey Drake Graham), with whom she collaborated on his song and video, "Take Care."