St. Bertin (c. 615 – c. 709) is a saint and abbot of Saint-Omer.

He was born near Coutances. At an early age he entered the monastery of Luxeuil in France where, under the austere rule of St. Columbanus, he prepared himself for his future missionary career. About the year 638 he set out, in company with two confrères, Mummolin and Ebertram, for the extreme northern part of France in order to assist his friend and kinsman, Bishop St. Omer, in the evangelization of the Morini. This country, now in the département of Pas-de-Calais, was then one vast marsh, studded here and there with hillocks and overgrown with seaweed and bulrushes. On one of these hillocks, Bertin and his companions built a small house whence they went out daily to preach the word of God among the natives, most of whom were still heathens.

Gradually some converted heathens joined the little band of missionaries and a larger monastery had to be built. A tract of land called Sithiu had been donated to Omer by a converted nobleman named Adrowald. Omer now turned this whole tract over to the missionaries, who selected a suitable place on it for their new monastery. Additional villages were granted by Count Waldebert, later a monk at Bertin's monastery of Sythiu and eventually abbot of Luxueil and canonized, who gave his son at the baptismal font to Bertin, from whom the boy received his name and his education. The community grew so rapidly that in a short time this monastery also became too small and another was built where the city of St. Omer now stands.