Flussio (pronounced: Flussìo, Frussìo in Sardinian) is an Italian municipality of 418 inhabitants in the province of Oristano, located in the ancient region of Planargia, in Sardinia. The town is linked to Tinnura, a municipality with which it shares the main road that corresponds to State Road 292.
The territory was already inhabited in Nuragic and Roman times. In the Middle Ages it belonged to the Giudicato of Torres and was part of the curatoria of Planargia. At the fall of the Giudicato (1259) it was governed by the Malaspina family and later (1308) became part of the Giudicato of Arborea. At the fall of the Giudicato (1259) it was governed by the Malaspina family and later (1308) became part of the Giudicato of Arborea. Around 1420, it came under the rule of the Aragonese Kingdom of Sardinia and became a feud, initially granted to the Villamarina family, to then be incorporated in the 18th century together with Suni (a more recent village) into the marquisate of Planargia, feud of the Paliaccio family. It was redeemed from the last feudal lords in 1839 with the suppression of the feudal system.