Saddle River (Passaic River)
- for the municipalities named for the river, see Saddle River, New Jersey and Upper Saddle River, New Jersey
The headwaters of the Saddle River are in the piedmont terrain of Rockland County, in southern New York state. Streams from this area flow south, forming the Saddle River at their confluence, two miles south of the New York state border, in the town of Upper Saddle River, New Jersey.
From its feeder streams in Upper Saddle River and the source in Airmont, New York, the Saddle River continues south for 16.3 miles, passing through the towns of Saddle River, Waldwick, Ho-Ho-Kus, Ridgewood, Glen Rock, Paramus, Fair Lawn, Rochelle Park, Saddle Brook, Lodi, Garfield, and Wallington.
The Ho-Ho-Kus Brook, a major tributary, joins the Saddle River at the Dunkerhook area of Saddle River County Park. Their confluence marks the border of four Bergen County towns: Ridgewood, Paramus, Glen Rock and Fair Lawn.
Fish species in the Saddle River include largemouth bass, pickerel, bullhead catfish, sunfish and different varieties of trout. Most of the trout are stocked by the New Jersey Division of Fish and Wildlife , although the uppermost reaches of the river and some of its tributaries hold wild brown trout. These wild trout are threatened by increased residential use of lawn fertilizer which contributes to algae and weed growth.