A drunken teen slugged a cop at a Staten Island St. Patrick’s parade Sunday afternoon, authorities said.

The officer was attempting to control a crowd of unruly teens when Nicholas McGowan, 19, punched him in the face, police said.

The cop was taken to Richmond University Medical Center with a cut near his right eye.

McGowan, who allegedly was carrying a gravity knife, was charged with assault, criminal mischief and resisting arrest.