Authorities are on the hunt for an arsonist accused of setting a homeless man on fire, leaving him hospitalized after the incident occurred on a No. 3 train in Manhattan.

Surveillance footage from the MTA captures the suspect, who was seen wearing a grey jacket, black hat, black pants, black boots, and carrying a black backpack, as he moved through a city subway station.

The chilling event unfolded as the 56-year-old victim was asleep on a northbound train. The suspect boarded the train just as the doors opened at the 34th St.-Penn Station stop in Midtown around 3:05 a.m. on Monday, according to police reports.

Once on the train, the suspect allegedly ignited the sleeping man’s clothing before swiftly exiting the carriage, leaving the victim to suffer the consequences as the train continued its journey.

It was an off-duty conductor who first noticed the alarming sight of smoke rising from the victim when the train reached the Times Square station, a mere five minutes later. The conductor promptly informed the authorities.

Responding police officers at the station acted quickly, using water to douse the flames and bring the situation under control, according to sources.

Medics rushed the victim to NewYork-Presbyterian/Weill Cornell Medical Center for treatment of severe leg burns, cops said.

The suspect fled the scene on foot before boarding a northbound No. 3 train, according to police, but an NYPD spokesman could not say how far he traveled on foot or where he boarded the train.

Anyone with information can phone in tips to the NYPD’s Crime Stoppers Hotline at 1-800-577-8477.