Mazon is a village in Mazon Township, Grundy County, Illinois, United States. The name derives from the Potawatomi word for "nettles". The population was 979 at the 2020 census. Illinois' State Fossil, the unique and bizarre Tully Monster was first found in nearby Mazon Creek. Mazon was formerly served by the Santa Fe railway at the Mazon Depot. It was established in 1876.