The province of Oristano is a province in the autonomous island region of Sardinia, Italy. Its capital is the city of Oristano. There are 87 comuni …The province of Oristano is a province in the autonomous island region of Sardinia, Italy. Its capital is the city of Oristano. There are 87 comuni in the province. 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.