A man jumped to his death from a historic Upper West Side apartment building early Monday night, authorities said.

The victim, in his 50s, plunged from the top floor of the Apthorp, on Broadway near West 78th Street, at about 4:30 p.m. and landed on top of scaffolding erected on the street.

The victim’s distraught companion wailed outside of the building.

“His girlfriend ran out of the building screaming, ‘That’s my boyfriend,’” a witness said.

Apartments at the swanky 12-story prewar residence can fetch up to $12 million.