South Amboy is a city in Middlesex County, New Jersey, on the Raritan Bay. As of the 2010 United States Census, the city's population was 8,631, reflecting an increase of 718 from the 7,913 counted in the 2000 Census, which had in turn increased by 50 from the 7,863 counted in the 1990 Census.South Amboy and Perth Amboy, across the Raritan River, are collectively referred to as The Amboys. Signage for exit 11 on the New Jersey Turnpike refers to "The Amboys" as a destination.