An 11-year-old girl was groped at knifepoint by a pervy passenger aboard a Bronx train, police said. 

The preteen was on a northbound No. 4 train as it approached the East 149th Street-Grand Concourse station in Mott Haven around 3:30 p.m. Oct. 18 when the sickening stranger approached her, cops said. 

The man — depicted in an NYPD sketch Wednesday — flashed a knife and, speaking in Spanish, told the girl to be quiet, authorities said. 

He then caressed the girl’s leg, waist and buttocks, cops said. 

Described as about 40 years old and around 5 feet tall, the man got off the train at the 161st Street-Yankee Stadium train station. 

The girl did not report any physical injuries after the frightening encounter.