A maniac sucker-punched a 75-year-old woman in the back and knocked her to the ground inside an East Harlem train station early Tuesday, cops and sources said.

The 75-year-old woman was standing on the Nos. 4, 5, and 6 train platform at 125th Street around 12:30 a.m. when she spotted a man acting bizarrely moments before the unproked attack, authorities and sources said.

The stranger then punched her in the back, a blow that sent her tumbling onto the platform, hitting her face, the sources said.

The assailant ran off, and the victim went to Mount Sinai Morningside to be treated for a cut on her lip and bruising, cops said.

No arrests had been made by Tuesday evening.

The random attack came one day after a stranger randomly slugged a 28-year-old woman as she stepped off a No. 3 train at West 96th Street on the Upper West Side, police said.

And on Sunday evening, a 25-year-old man was slashed on the arm by a crazed commuter who had been mumbling to himself on the uptown F train platform at Second Avenue and East Houston Street, cops and sources said.

Despite the recent rash of violence, overall felony assaults in the subway system have dropped about 5% so far this year – down to 449 from the 471 reported at this time in 2023, according to the latest data, updated Sunday.

A total of 1,210 misdemeanor assaults have been reported, about a 1% dip from the 1,226 tallied at this point last year.