A 56-year-old man is believed to have jumped to his death from a tony Upper East Side building Tuesday morning, authorities said.

The man – who was not immediately identified – is thought to have leaped from the fourth floor of 18 East 67th Street, just steps away from the coveted high-end shopping stretch of Madison Avenue, police said.

He was found on the sidewalk at 7:19 a.m., and was pronounced dead on arrival at Weill Cornell Medical Center.

The man left a suicide note, according to police at the scene.

By 9 a.m., the area around the scene was still cordoned off while police talked to the building’s superintendent.

A window on the top floor of the building appeared to be about a quarter of the way open – though it was not clear if that was where the man jumped from.

The East 67th Street address was built in 1905 and has eight units – including a three-bedroom, two-bathroom apartment that rented for $9,000 per month last year, according to StreetEasy.

If you are struggling with suicidal thoughts, you can dial the 24/7 National Suicide Prevention hotline at 988 or go to SuicidePreventionLifeline.org.