Marlboro is a hamlet (and census-designated place) in Ulster County, New York, United States.

The Chapel Hill Bible Church, Christ Episcopal Church, Dubois-Sarles Octagon, Elliot–Buckley House, and Shady Brook Farm are listed on the National Register of Historic Places.

[2][3][4] Marlboro is also the location of the Gomez Mill House, an historical site which is the oldest Jewish residence in Ulster County.

There were 981 housing units at an average density of 354.9 per square mile (137.0/km2).

28.2% of all households were made up of individuals, and 12.3% had someone living alone who was 65 years of age or older.