The monastery of Santa María de Monfero was founded in 1134 by the nobles Alfonso Bermúdez and his nephew Pedro Osorio. It was entrusted to the Benedictines until 1147, when it joined the Cistercian Order under the Abbey of Sobrado.
From the 13th century the abbey grew through lay brothers. This expansion led to conflicts with feudal lords, requiring royal intervention in the 14th century.
Its period of greatest splendour came in the 16th and 17th centuries, when cloister, refectory, gatehouse and church were rebuilt in Baroque style.
In 1820 all monks were expelled. The monastery was declared a Historic-Artistic Monument in 1931. Restoration campaigns have been ongoing since the 1960s. In 2003 it was transferred to the Xunta de Galicia for fifty years, with possible renewal.