Castropol is a municipality in Asturias, Spain. It is also the name of a parish within the municipality and a town within the parish.The municipality of Castropol has a population of 3696 (INE, 2014). It is bounded on the north by the Cantabrian Sea and on the west by a coastal inlet, or ria, which separates it from the municipality of Ribadeo in Galicia.