The Tirso (Sardinian: Tirsu, Latin Thyrsus) is a 152-kilometre (94 mi) river, the most important of the island of Sardinia (Italy). It rises from the plateau of Buddusò, on the slopes of the Punta Pianedda at an elevation of 985 metres (3,232 ft) and crosses the island from east to west, passing through Lake Omodeo and entering the sea in the Gulf of Oristano.