The Ramapo River is a tributary of the Pompton River, approximately 30 mi (48 km) long, in southern New York and northern New Jersey in the United States.
It rises in mountainous area of central Orange County, New York, near Monroe and flows southeast to Harriman, then south into western Rockland County, then into northern Bergen County, New Jersey. In New Jersey, it flows SSW, along the west side of the ridge of the Ramapo Mountains. It joins the Pequannock River near Pompton Plains to form the Pompton River.
The river is a popular destination for fly fishing of trout. The New York State Thruway follows the valley of the river in Orange County.
