Mountain Avenue is an active commuter railroad station in the township of Montclair, Essex County, New Jersey. Serving trains of NJ Transit's Montclair-Boonton Line, Mountain Avenue is one of six stops in the municipality. The next station to the south/east is Upper Montclair. The next station to the north/west is Montclair Heights. Mountain Avenue contains two low-level side platforms. The station depot built by the Erie Railroad stands on the inbound platform, offering a waiting room for commuters. Part of the depot is also leased by the municipality for a residence.

Montclair is a township in Essex County in the U.S. state of New Jersey. Situated on the cliffs of the Watchung Mountains, Montclair is a commercial and cultural hub of North Jersey and a diverse bedroom community of New York City within the New York metropolitan area. The township is the home of Montclair State University, the state's second-largest university.