A crazed subway rider slashed another straphanger across the ear for allegedly staring at him as they rode on a Manhattan subway train, cops said.

A 23-year-old victim whose identity was not released by police, was riding an uptown 2 train at 12:30 a.m. when he was confronted by another straphanger in Harlem.

The perp, a man police describe as having a dark complexion and standing 6 feet fall, accused the rider of having stared at him disrespectfully, which led to an argument, cops said.

When the train pulled into the West 135 Street station, the two men got off the train to fight, authorities said.

The rider then slashed the 23-year-old man’s ear while the two were standing on the platform. The slasher then hopped on a northbound 2 train and disappeared, cops said. 

The 23-year-old man was later transferred to Harlem Hospital in stable condition, according to police.