Shocking surveillance video shows the moment a thug clobbered a 90-year-old man over the head with a cane in an unprovoked attack on a Manhattan sidewalk.

The elderly victim was walking on Broadway near West 204th Street in Inwood just before 6 p.m. on Friday when the attacker suddenly approached and kicked his shopping cart before walloping him on the side of the head with the cane.

Good Samaritans stepped in to stop the assault — but the suspect got away, fleeing west on Broadway, cops said.

First responders rushed the apparently innocent victim to a local hospital for cuts to his ear and head. He is in serious but stable condition.

The attacker is between 20 and 30 years old, around 5-foot-9 or 10 and about 150 pounds. He was wearing headphones, a blue baseball cap, a black shirt, a gray long-sleeved shirt, blue pants with checker-box print and black sneakers, cops said.