The Southern State Parkway (also known as the Southern State or Southern Parkway; abbreviated as SO on signage) is a 25.53-mile (41.09 km) limited-access highway on Long Island, New York, in the United States. The parkway begins at an interchange with the Belt and Cross Island parkways in Elmont, in Nassau County, and travels east to an interchange with the Sagtikos State Parkway in West Islip, Suffolk County, where it becomes the Heckscher State Parkway. The Southern State Parkway comprises the western portion of unsigned New York State Route 908M (NY 908M), with the Heckscher Parkway occupying the eastern section.