An inmate has been caught on video slashing a correction officer across his face after a battle involving as many as a dozen prisoners at Rikers Island.

The vicious Friday night attack took place in a dorm-style housing area in the Anna Cross Center, according to the officers’ union, the Correction Officers Benevolent Assn.

Names of the victim and the suspected slasher, who is believed to be a member of the Bloods gang, were not immediately released.

Officers used pepper spray to break up the battle.

When the fight ended, one of the inmates followed an officer to a door and used a blade to inflict a three-inch wound on him.

“This inmate has been re-arrested for this attack on our officer who was trying to keep this inmate safe after a fight with other inmates,” said Peter Thorne, spokesman for the Department of Correction.

It’s not clear what offense the inmate had been jailed for.

At a Saturday press conference, COBA president Elias Husamudeen blasted Governor Cuomo, Mayor de Blasio and the City Council as “unable or unwilling to protect the lives of correction officers who took an oath to protect inmates in our custody.”

Husamudeen argued that since the inmate population is “lower than it has ever been,” the inmates should be spread out, making jails smaller and easier to control.

“Instead [de Blasio] is piling the inmates on top of each other in our facilities and sending correction officers in these gang-infested jails, and saying ‘protect the inmates,’ and at the same time removing the very tools we need to do that job,” he said.