An 18-year-old woman was fatally struck by a train early Tuesday after she suffered a sudden medical episode and fell onto the tracks at a Queens subway station, cops said.

The teenager collapsed at the Roosevelt Avenue-74th Street station in Jackson Heights around 6:40 a.m., and fell onto the Manhattan-bound E train tracks, authorities said.

She was discovered lying on the roadbed, unconscious and unresponsive, with trauma to her body, police said. 

The young woman – who was traveling alone – was pronounced dead at the train station by EMS workers.

A witness told cops that the girl suffered an unspecified medical episode that apparently caused her to lose her balance and tumble onto the tracks – and into the path of the oncoming train, police said. 

Her name was not immediately released, pending family notification.

The tragic incident snarled subway service on the E, F and R lines, through the rush hour commute.