Omer, also called Audomar, was a Frankish monk and missionary bishop of the seventh century who is venerated as the apostle of the region of the Morini in northern Gaul. Born into a distinguished family in the territory of Coutances in Neustria toward the close of the sixth or beginning of the seventh century, he became a monk of Luxeuil before being raised to the see of Therouanne, where he devoted nearly thirty years to converting a largely pagan population and covering the region with monastic foundations. He is commemorated on September 9.
After the death of his mother, Omer entered the abbey of Luxeuil in the Diocese of Besancon, by tradition around 615, persuading his father to accompany him. They distributed their possessions to the poor and were tonsured together, and Omer studied the Scriptures under the direction of the abbot Eustachius, in which he is said to have acquired remarkable proficiency.
When King Dagobert sought a bishop for Therouanne, the ancient capital of the Morini, Omer was consecrated for that see in 637. He found most of the inhabitants still pagan, and the few remaining Christians lapsed for lack of priests. With a group of disciples drawn from Luxeuil, he set about the conversion of the region and established monasteries that became centers of learning, so that the diocese came to be reckoned among the most flourishing in Gaul.
In his old age Omer became blind, after governing his church for nearly thirty years, yet by the accounts of his life this affliction did not lessen his pastoral care for his flock. The exact date of his death is unknown; he is believed to have died about the year 670. The monastery he founded grew into the town of Saint-Omer, which bears his name to this day.