A man who saved a young woman from being crushed by an L train in Union Square Monday night after she fainted and fell onto the tracks has vanished.

The good Samaritan jumped onto the tracks and rescued Jessica Oshita, 26, when she suddenly fell onto the tracks.

Oshita was reportedly left unconscious and lying face-down on the tracks with blood pouring from her head.

At first, the man tried to lift Oshita onto the platform, however with the impending rumble of the train in the distance, witnesses say the hero placed Oshita's body in the well between the rails and then hoisted himself into the platform.

Police say the man has only been described as black and that he disappeared quickly after the incident.

Five subway cars ran over Oshita's body and she suffered three facial lacerations. She was rushed to Bellevue Hospital yesterday and was listed in stable condition.