A man was arrested for fondling himself in front of a teen on a New Jersey bus, authorities said.

Donn M. Ronquillo was sitting across from the 15-year-old victim when he began pleasuring himself around 2 p.m., police said.

The victim cried out for help and the bus driver alerted Port Authority police who arrested Ronquillo in Jersey City between Bergen and Sipp Avenues, cops said.

Ronquillo, 37, was taken to Hudson County Correctional Facility on Friday and charged with aggravated criminal sexual contact.