Marlboro is a hamlet in Ulster County, New York, United States. The population was 3,669 at the 2020 census. Marlboro is in the southeastern part of the town of Marlborough, located in the southeastern corner of the county.

The Gomez Mill House is located in the Town of Newburgh, New York, USA, on Mill House Road a short distance off US 9W, just south of the Orange–Ulster county line. Over 300 years old, it is the earliest known surviving Jewish dwelling in North America and the oldest home in Orange County listed on the National Register of Historic Places.