Fordongianus, (Sardinian: Fordongianis) (Ancient Greek: Hydata Hypsitana, Latin: Aquae Hypsitanae or Forum Trajani,) is a comune (municipality) in the Province of Oristano in the Italian region Sardinia, located about 90 kilometres (56 mi) northwest of Cagliari and about 25 kilometres (16 mi) northeast of Oristano. As of 31 December 2004, it had a population of 1,037 and an area of 39.4 square kilometres (15.2 sq mi). Fordongianus borders the following municipalities: Allai, Busachi, Ghilarza, Ollastra, Paulilatino, Siapiccia, Villanova Truschedu.