Portomarín is a municipality in the Spanish province of Lugo. It has a population of 2008 (Spanish 2001 Census) and an area of 115 km². It is part of El camino francés de Santiago.
In the 1960s the Miño River was dammed to create the Belesar reservoir, putting the old village of Portomarín under water. The most historic buildings of the town were moved brick by brick and reconstructed in the new town, including its castle-style main church: Church of San Juan of Portomarín.