A Brooklyn fare-beater allegedly punched a young woman in the face while apparently playing the “knockout game” in a Manhattan PATH station — and her friend chased him down, put him in a chokehold and forced him to apologize, sources said.

Ibrahim King, 36, allegedly slugged 21-year-old Elizabeth Mejia, breaking her orbital bone, in the Ninth Street station around 3:40 a.m. Sunday.

“He looks at her for a very short moment and then he pulls his right fist back and lunges across the railing and punches her in the face,” said Mejia’s friend Steve Sala.

Sala chased and grabbed King, then put him in a chokehold, ripping out one of his dreadlocks in the process.

“I asked him repeatedly if he thought it was funny and asked him if he was sorry,” said Sala, 21. “He finally apologized, but not right away.”

King squirmed out of the chokehold and tried to escape, but was tracked down by Port Authority detectives.

He was charged with assault.

Mejia was taken to Bellevue Hospital, where she was treated for fractures to her left orbital bone and her nose.