Three thrift store employees overpowered a robber who was wielding a shotgun in Long Island — including a woman who grabbed the weapon and beat the robber about the head with it, cops and witnesses said Sunday.

Ronald J. Kelly walked into Island Thrift store carrying the firearm around 8:25 p.m. Saturday, and demanded the store manager empty the til, according to the Suffolk County Police Department.

The woman grabbed the gun, and with the help of two other employees managed to wrestle him to the ground.

“She grabbed the gun and started struggling with the guy,” store manager Rich Rodriguez told The Post. “The two male employees saw what was going on and started punching the guy in the face. She grabbed the shotgun and started hitting him in the face with the butt of the gun.”

“She’s very brave,” Rodriguez added of the woman who wasn’t identified.

The trio managed to pin Kelly to the floor until cops arrived.

None of the workers were injured, but the accused robber suffered scratches and bruises that made for a nasty mugshot. He was transported to Stony Brook Hospital for treatment, cops said.

Kelly, 45, was charged with first-degree robbery and criminal possession of a controlled substance.