Hai'an County (海安 县) is a district of the district-free city of Nantong in Jiangsu Province, China. It has an area of ​​1,110 km² and has 960,000 inhabitants. Its main town is the large community Hai'an (海安 镇). The Neolithic Qingdun site (Qingdun Yizhi 青墩 遗址) has been on the list of monuments of the People's Republic of China (6-75) since 2006.