Monterreal Castle is a castle in Ría de Vigo and the valley of Miñor (Val Miñor), Galicia, Spain.
Construction of Monterreal Castle began in the 12th century and was completed in the 16th century, and now serves as a tourist attraction. Three of the castle's towers are preserved: the Reloj tower, the Tenaza tower with a heptagonal base and the Príncipe tower. The first appearance of the castle in record dates from the year 60, when Julius Caesar conquered Baiona. Apart from the Romans, the Visigoths and Muslims also left their marks in the Monterreal Castle, whose name was given by the Catholic Monarchs.
The Castle is defended by the Puerta del Sol, a ramp with a lifting bridge and the three large towers.