A 49-year-old man was found dead with stab wounds to the neck in the basement of a sleek lower Manhattan hotel Sunday morning, cops said.

The man was unresponsive and unconscious when cops found him inside a bathroom in the basement of the Public Hotel shortly after 11 a.m., authorities and law enforcement sources said.

The deceased, who was not a registered guest at the Bowery hotel, was found with a knife next to him, sources told The Post.

He was pronounced dead at the scene, police said.

It was immediately not clear if the puncture wounds were self-inflicted or the result of a homicide. No arrests have been made, cops said.

The Office of the Chief Medical Examiner will determine the cause of death, the NYPD said. The investigation is ongoing and the identity of the man will be released pending family notification.

The man’s body was found after a large wedding celebration was held on the roof of the hotel — where a stay costs between $200 and $400 a night — the night before, guests told The Post on Sunday afternoon.

An alarm also went off on Saturday night before 11 p.m. with an ensuing announcement that stated to disregard it and that there was no emergency, guests said. It’s unclear if the alarm was at all related to the stabbing — or when the man suffered the knife wounds.

Hotel staff was instructed not to talk to a Post reporter who was there Sunday afternoon.

The Public Hotel offers multiple bars, restaurants, and workout classes open to the public. Its amber glowing escalators often appear as a backdrop on visitors’ Instagram photo-ops and were even featured on a past season of Saturday Night Live’s opening credits.