Straphanger, 51, on life support after stranger punches him to ground in Times Square subway

A 51-year-old straphanger is on life support after a stranger punched him down to the ground during a dispute inside the Times Square subway station Wednesday, cops and sources said.

The victim got into a dust-up with another man around 6:45 p.m. on the mezzanine for the N, Q and R trains at the 42nd Street-Times Square station, authorities said.

The feud turned violent when the menace slugged the victim in the face, causing him to fall and hit his head on the ground, police sources said.

Responding cops found the victim with trauma to his face and rushed him to Bellevue Hospital, where he was listed in critical condition – on life support in the intensive care unit, cops and sources said.

The attacker, described as a man with a dark complexion, wearing a gray polo short and blue jeans and carrying a black backpack, was still on the loose by the afternoon.

It remained unclear what sparked the burst of violence.