Marrubiu (Sardinian: Marrùbiu) is a comune (municipality) in the Province of Oristano in the Italian region Sardinia, located about 70 km northwest of Cagliari and about 15 km south of Oristano. As of 31 December 2004, it had a population of 5,034 and an area of 61.2 km². Marrubiu borders the following municipalities: Ales, Arborea, Morgongiori, Santa Giusta, Terralba, Uras.