The 19-year-old victim was on a No. 1 train at 181st Street in Washington Heights around 12:30 a.m. with her boyfriend, when a man approached and asked both of them for the time, police said.
He repeated the question multiple times, but they ignored him, cops said.
The man briefly turned away from the two straphangers, but then turned back and knifed the teen on the arm, police said. She was taken to New York-Presbyterian Hospital-Columbia in stable condition.
The suspect fled from the train at 168th Street, police said. At least three other people were stabbed in Upper Manhattan and the Bronx overnight, police said.
About 15 minutes after the subway attack, a 39-year-old man was stabbed in the neck during a dispute with another man on University Avenue near West Kingsbridge Road in the Kingsbridge Heights section of the Bronx, cops said.
He went to St. Barnabas Hospital in stable condition, and the suspect took off, police said. A 52-year-old man was also stabbed in the upper right arm at Amsterdam Avenue and West 145th Street, also in Hamilton Heights, around 9:50 p.m. Wednesday, cops said.
The motive was not immediately known.