Allai (Sardinian: Àllai) is a comune (municipality) in the Province of Oristano in the Italian region Sardinia, located about 80 kilometres (50 mi) north of Cagliari and about 25 kilometres (16 mi) east of Oristano. As of 31 December 2004, it had a population of 409 and an area of 27.4 square kilometres (10.6 sq mi).
Allai borders the following municipalities: Busachi, Fordongianus, Ruinas, Samugheo, Siamanna, Siapiccia, Villaurbana.