A Suffolk County cop was arrested Monday for seriously injuring a motorcyclist in a hit-and-run Sunday night, authorities said.

Officer Thomas O’Neill, 44, was attempting to turn left into a parking lot in Ronkonkoma when his pickup truck hit Charles Giardinello, 40, who was riding a motorcycle, at around 7:25 p.m., cops said. The officer then allegedly fled.

Giardinello was listed in critical condition at Stony Brook University Hospital.

O’Neill, of Centereach, was charged with leaving the scene of an incident after he turned himself in at the Fourth Precinct station house in Smithtown Monday morning, police said.