An unidentified woman was struck by an oncoming No. 6 train and severely injured Saturday afternoon in Midtown, cops said.

The train hit the woman — who was on the tracks, according to police — around 5:34 p.m. at the Grand Central-42nd St. subway station. It was unclear how she wound up on the tracks.

EMS transported her to Bellevue Hospital where she was in critical condition.

Police are investigating if any criminality was involved. No arrests have been made in the incident.