San Xoán de Poio is a former Benedictine monastery that is currently occupied by a Mercedarian community. Its origins are uncertain, and some have even attempted to link its foundation to Saint Fructuosus of Braga, a hypothesis that must be dismissed. It is known that the monastery received financial endowments from King Bermudo II (953-999) and Queen Urraca in the year 1116. In 1154, Pope Anastasius IV confirmed its possessions.
Later, the monastery became linked to the Archdiocese of Santiago as a result of a donation made by Ferdinand II in 1169. By the late 15th century, the establishment was in decline, as evidenced by a visit in 1494 that reported a chaotic situation. However, the situation was later reversed: in 1547, it was incorporated into the Congregation of Valladolid, and in 1548, a prestigious theology college was founded there. It remained a Benedictine community until 1835, when the disentailment led to its closure.
From 1890 onward, the monastery was occupied by the Mercedarians, who are still present today. No remains of the original buildings have survived; the current monastery corresponds to the structure built between the 17th and 18th centuries. After the exclaustration, it was abandoned until it was restored by the Mercedarians in the late 19th century.
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