A Bronx man is clinging to life when he was attacked by a person dressed up as Batman at a Riverdale bar’s Halloween party Saturday, police sources said.

The victim, 24, got into a fight at Fenwick’s Bar and Grill on West 238th Street, and was beaten by at least seven assailants, who are still at large, a police source told the Post.

The beat-down started after an argument with the partygoer in the Batman costume, and the victim was left with a head injury.

Although he did not go to the hospital immediately, doctors at Columbia Presbyterian discovered Sunday that the young man was still bleeding into his brain, the source said.