A man was found dead on the exit ramp of a Staten Island highway with a gunshot wound to the head on Monday night, police said.

Police discovered the body on the exit ramp of the Staten Island Expressway near Slosson Avenue in Castleton Corners at about 11:45 p.m., cops said.

Medics rushed the gunshot victim to Richmond University Medical Center, where he died, authorities said.

Cops initially believed the man was struck by a car, but later determined he was shot to death, a police source said.

It’s not clear how he got on the exit ramp of the expressway, authorities said.

Police are investigating the circumstances that led to the shooting. No arrests were made Monday night, cops said.