New York State Route 878 (NY 878) is an expressway on Long Island and in New York City. The route exists in two sections, which both form the Nassau Expressway. NY 878's western terminus is the Belt Parkway and Conduit Avenue (NY 27) in Ozone Park, within southern Queens. Its southern terminus is immediately before the Village of Atlantic Beach, at the Atlantic Beach Bridge in Lawrence, within southwestern Nassau County. NY 878 is discontinuous between Farmers Boulevard in Queens and the town of Inwood in Nassau County. The two sections are connected to each other by Rockaway Boulevard and Rockaway Turnpike.

The Belt Parkway is the name given to a series of controlled-access parkways that form a belt-like circle around the New York City boroughs of Brooklyn and Queens. The Belt Parkway comprises three of the four parkways in what is known as the Belt System: the Shore Parkway, the Southern Parkway, and the Laurelton Parkway. The three parkways in the Belt Parkway are a combined 25.29 miles (40.70 km) in length. The Cross Island Parkway makes up the fourth parkway in the system, but is signed separately.