A stranger pummeled a straphanger who confronted him for harassing a woman on a Queens train over the weekend, cops said. 

The 27-year-old victim was riding a southbound No. 7 train around 12:40 a.m. Sunday when he spotted a man bothering a female passenger, authorities said. 

The victim intervened — setting off the other man, who punched him multiple times in the face, police said. 

The assailant got off the train when it stopped at 90th Street-Elmhurst Avenue and fled onto the street, according to police. 

The victim was taken to Elmhurst Hospital Center for a nose injury and a cut on his face, authorities said. 

The NYPD late Monday released photos of the suspect inside the train car. 

He was still being sought Tuesday morning.