O Porriño is a municipality in the province of Pontevedra, in the autonomous community of Galicia, Spain. It belongs to the comarca of Vigo. As an industrial town in the Vigo metropolitan area, it has an important economic significance. One of its main industries is granite production; the variety of granite produced in O Porriño is known as Rosa Porriño, and is exported from the Port of Vigo mainly to Italy, Japan and China.