The Abbey of St. Bertin was a Benedictine abbey in Saint-Omer, France, now in ruins (the town's town-hall was built with stone from the abbey in 1834) and open to the public. It was dedicated to its second abbot, Saint Bertin.
The monastery was founded on the banks of the Aa in the 7th century by the bishop of Thérouanne, who sent the monks Bertin, Momelin and Ebertram from Omer to proselytize among the pagans in the region. The Abbey of St. Bertin soon became one of the most influential monasteries in northern Europe and ranked in importance with Elnon Abbey (later Saint-Amand Abbey, in Saint-Amand-les-Eaux) and the Abbey of St. Vaast. Its library included the codex of Aratea of Leyde, from which two copies were made.
Already in the 9th century the abbey had a priory in Poperinge. A Romanesque church was constructed in the mid-11th century.[1] It was 25m high, with a 48m high tower, and included a large 14th century semi-circular sanctuary with five side-chapels. It served as a model for the church, whose construction was not completed until the beginning of the 16th century.
From the 12th century the abbey had the right of appointing the priest at Lissewege and Ruiselede (1106). William Clito was buried here in 1128. The abbey had a 'refuge-house' in the now-demolished Sint-Lodewijkscollege in Bruges. The abbey had its greatest flourishing from its inception until the 13th century, though it survived until it was shut down at the French Revolution.
In 1830 the commune demanded the demolition of the church, though they spared the tower, which they strengthened with a buttress in the nave (still visible). However, the tower was weakened by bombardment of the town centre in World War II and collapsed in 1947, leading to the abandonment of the site.
The abbey is known for its Latin-written carticulary (Chartularium Sithiense) whose first part is attributed to Folquin (or Saint Folquin, died 14 December 855 in Esquelbeques).