Monsey is a hamlet and census-designated place, in the town of Ramapo, Rockland County, New York, United States located north of Airmont; east of Viola; south of New Hempstead; and west of Spring Valley. The village of Kaser is completely surrounded by the hamlet of Monsey. The 2010 census listed the population at 18,412.
Rockland County was inhabited by the Munsee band of Lenape Native Americans, who were speakers of the Algonquian languages. Monsey Glen, an Indian encampment, is located west of the intersection of State Route 59 and State Route 306. Numerous artifacts have been found there and some rock shelters are still visible. The Monsey railroad station, which received its name from an alternate spelling of the Munsee Lenape, was built when the New York & Erie Railroad passed through the glen in 1841.In the 1950s, Monsey was a one stoplight town with a single yeshiva. By 1997, Monsey had 112 synagogues and 45 yeshivas.Located near Monsey is the Houser-Conklin House, listed on the National Register of Historic Places in 2010.