Some authors already speak of its existence at the time of San Martiño Monastery of Dumio in the sixth century; others attribute its foundation to St. Fructuosus of Braga a century later. However, the failure of documents that are graduating should situarmo us in the twelfth century to find references to a monastic community in place. This community belongs to Order of Saint Benedict was to be the result of the merger of three existing communities in the region: Oia, another of Saints Cosmas and Damian situated above the village of Erizana and a third in San Mamede de Loureza. In this way, according to Manrique, you can place the monastery's founding in 1137, incorporating to the Cistercian Order in 1185.