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 (+9.1%) from the 7,913 counted in the 2000 Census, which had in turn increased by 50 (+0.6%) from the 7,863 counted in the 1990 Census.
South Amboy has passed through three of the five types of New Jersey municipalities. It was first mentioned on May 28, 1782, in minutes of the Board of chosen freeholders minutes as having been formed from Perth Amboy Township, and then formally incorporated as a township on February 21, 1798. Over the next 90 years, portions broke away to form Monroe Township (April 9, 1838), Madison Township (March 2, 1869; later Old Bridge Township) and Sayreville Township (April 6, 1876; later Borough of Sayreville). As of February 25, 1888, South Amboy borough was formed, replacing South Amboy Township. On April 11, 1908, South Amboy was incorporated as a city, replacing South Amboy borough, with a referendum held on July 21, 1908.