Garret Mountain Reservation (also spelled Garrett) is a 568-acre (230 ha) park located on First Watchung Mountain (Garret Mountain) in Paterson and Woodland Park (formerly West Paterson) in southern Passaic County, New Jersey. In 1967, it was designated a National Natural Landmark as part of the Great Falls of Paterson-Garret Mountain listing. The park extends into Clifton. Garret Mountain is Passaic County's major recreational area, providing the visitors with grass fields, several miles of walking/running trails, basketball courts, picnic areas, Barbour's Pond is state stocked with fish for anglers, as well as an Equestrian Center with horseback riding lessons.

The Passaic County Parks Department operates the park while the Passaic County Sheriff is responsible for law enforcement in the reservation. For the past several decades, the reservation has been the site of hundreds of high school and college cross country meets in the fall, including the New Jersey State Interscholastic Athletic Association (NJSIAA) High School State Sectional Championships at the end of every October.