Cops nabbed a would-be thief who punched a woman after she refused to fork over her phone in Grand Central Saturday afternoon.

The 58-year-old victim was on the stairs of the transit hub — near the 4, 5 and 6 train lines — when the attacker confronted her around 1:30 p.m., police said. When the plucky victim kept a hold of her phone, the fiend allegedly struck her before taking off.

The victim followed her assailant out onto the street, where she notified police of the incident, cops said.

Police found the 35-year-old slugger about 10 minutes later and arrested him. Charges are pending.