A creep is on the loose after groping a teenage girl inside an Upper West Side subway station Wednesday night, the NYPD said.

The low-life targeted the 16-year-old as she was standing on the 96th Street station’s northbound “1” train island platform around 8:45 p.m., according to police.

He “grabbed her under the clothing” before fleeing the station — but not before flipping off a straphanger who snapped his picture.

The alleged molester’s face was hidden by a mask, the image shows. He was wearing a black sweatshirt and sweatpants with a white undershirt.

His hair appeared half-shaven, with the longer strains braided down his neck.

The victim did not sustain any injuries and the investigation is ongoing.