An unhinged menace repeatedly stabbed a commuter in an unprovoked attack inside the Port Authority Bus Terminal early Monday, police sources said.

The victim was sitting and reading a book in the Greyhound area of the Midtown hub around 5:40 a.m. when the suspect approached and stabbed the person repeatedly, the sources said.

The injured straphanger was taken to Bellevue Hospital with non-life-threatening injuries, according to the sources.

The suspect, meanwhile, was arrested at the scene, the sources said.

No information was immediately known about the victim or the assailant.