Two top mixed-martial-arts fighters — part of the famed Gracie clan — were busted for helping to beat a bouncer to a pulp outside a Manhattan celeb hangout early Monday, law-enforcement sources told The Post.

Renzo Gracie and his cousin Igor were arrested along with five other people for the 1:30 a.m. beat-down of Craig Molesphini, 35, outside 1 OAK in the Meatpacking District, sources said.

The victim suffered a fractured right arm along with bruises and cuts, sources said.

“I’m OK,” Molesphini said later Monday. “I have a slightly fractured elbow.’’

The hulking cousins — whose Brazilian family started the sports-promoting business Ultimate Fighting Championship — were charged with gang assault, as were the other suspects. The charge for Renzo and Igor Gracie is in the second degree, according to Fox Sports.

The pair were released on $10,000 bail.

The cousins hold black belts in karate and specialize in jiu-jitsu, in which arm and leg locks and choke-holds are part of the “submission-based’’ martial art.

“People who train this kind of stuff have no business getting into street fights — it’s completely unfair,’’ said a disgusted law-enforcement source. “These guys really should have known better.”

Renzo, 47, who lives in New Jersey, has a gym in Midtown where he trains top UFC fighters. A son of Robson Gracie, his last official MMA bout was in 2010.

Igor, 34, is the son of Rolls Gracie and brother of Gregor Gracie. He has a training gym in New Rochelle.

The thugs were busted in front of the trendy West 17th Street club, where celebs such as Jay Z, Beyoncé, Leonardo DiCaprio and Cameron Diaz hang out.