Police are asking for the public’s help identifying a man who groped a teenage girl aboard the 4 train on Jan. 10 in Mott Haven.

Investigators say he approached the 19-year-old victim from behind and grabbed her backside as the southbound train approached the 149th Street Grand Concourse station.

The victim remained on board, while the man left the train and fled the scene on foot.

Police say the suspect was last seen wearing a black jacket, sweater and pants.

Anyone with additional information is urged to call 1-800-577-TIPS.