A woman was slashed several times by a complete stranger while they rode an MTA bus through the Bronx, police said Wednesday.

The 18-year-old victim and the man were riding a Bx 9 bus as it traveled on Fordham Road when he began arguing with her.

As the argument escalated, the teen got up to ask the bus driver for help — only for the man to follow after her, cops said.

Video released by police Wednesday shows the stranger approach the front of the bus behind the woman. He points at her as he appears to speak to someone off-camera.

Just moments later, the unhinged man pulled out a sharp object and slashed the teen in the face, neck and back, causing serious wounds and bleeding, police said.

The victim was taken to St. Barnabas Hospital, where she was treated and released.

Police are still looking for her attacker, who fled south on Webster Avenue.