Police are looking for a man they said approached an 81-year-old man from behind in the Bronx on last week before punching him in the face — an attack caught on surveillance video.

The man approached the victim around 11:10 p.m. last Sunday on Courtlandt Ave. near East 154th St. in Melrose, according to authorities.

The video shows the man walking behind the 81-year-old before swinging his arm around to punch the victim in the face, sending him to the ground before running away.

Police said the man suffered bruises to his face and was taken to a local hospital in stable condition.

Officials said the victim and the attacker did not interact before the assault.

The attacker was described as having curly black hair, last seen wearing a black shirt, black shorts, and black-and-white sneakers.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-8477, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com