The province of Oristano is a province in the autonomous island region of Sardinia, Italy. Its capital is the city of Oristano. It has an area of 3,04…The province of Oristano is a province in the autonomous island region of Sardinia, Italy. Its capital is the city of Oristano. It has an area of 3,040 square kilometres, a total population of 160,746, and a population density of 53.7 people per square kilometer. There are 87 comuni in the province.