Monsey (/ˈmʌnsi/, Yiddish: מאנסי, romanized: Monsi) is a hamlet and census-designated place in the town of Ramapo, Rockland County, New York, United States, north of Airmont, east of Viola, south of New Hempstead, and west of Spring Valley.

[3] Rockland County was inhabited by the Munsee band of Lenape Native Americans, who were speakers of the Algonquian languages.

[4] In 1943, Rabbi Shraga Feivel Mendlowitz purchased a property in Monsey with the intention to raise the education level of Torah teachers.

In 1979,[6] Rabbi Ezriel Tauber and a group of lay leaders purchased land in Monsey for the American campus of the Ohr Somayach Yeshiva.

Monsey is a major center of Orthodox Judaism in the United States, along with several other cities such as Kiryas Joel, Kaser, Spring Valley, and New Square.

[15] The migration to Monsey began in the late 1940s when New York City's Orthodox Jews were seeking affordable real estate for their quickly growing communities.

These spaces offered the possibility of moving en masse and establishing enclaves where they could lead lives based on halakha (Jewish religious law) without coming into regular conflict with non-Orthodox neighbors.

[17] On December 28, 2019, Monsey was the site of a mass stabbing in the home of a Hasidic rebbe of the Kosonyu sect who was hosting a Hanukkah party, leaving four injured and one dead.