A dirt-bike rider gave a cop a dangerous ride in the Bronx on Friday, dragging the officer several blocks when he was stopped for cruising around in the illegal vehicle, police said.

The cop spotted Dennis Castellar, 36, near Bruckner Boulevard and East 138th Street in Mott Haven around 9:20 p.m. Castellar initially got off his bike, but when the cop approached, he hopped back on, and somehow got latched on to the officer, dragging him about six blocks to St. Mary’s Street and Beekman Avenue, police said.

The injured cop was treated at Lincoln Hospital for a fractured right collarbone, police sources said.

Castellar, of Parkchester, was arrested and charged with assault on a police officer, reckless endangerment, vehicular assault and reckless driving, police said.