Mantua Township is a township within Gloucester County in the U.S. state of New Jersey, within the Philadelphia metropolitan area. As of the 2020 United States census, the township's population was 15,235, its highest decennial count ever and an increase of 18 (+0.1%) from the 15,217 recorded at the 2010 census, which in turn reflected an increase of 1,000 (+7.0%) from the 14,217 counted in the 2000 census. Mantua and surrounding Gloucester County constitute part of South Jersey.