A 27-year-old woman fended off a knife-wielding robber while walking through the Upper East Side on Tuesday night, cops said.

The attack happened around 9:45 p.m. at East 78th Street and Third Avenue, where an unknown man grabbed the victim from behind and put a knife to her throat, cops said.

“What money do you have?” the man snarled, according to police.

The woman pepper-sprayed the robber before he grabbed her purse and fled on Third Avenue, cops said.

Cops later caught up to the alleged robber, 25-year-old Darnell Green, and charged him with robbery, police said.