Bretannio was a fourth-century bishop of Tomi, a see located in the Byzantine Empire in what is now Constanța, Romania. Originally from Cappadocia, he began his leadership of the local church around 360. He is remembered for his resistance to the Arianism promoted by Emperor Valens during a military campaign against the Goths. Although the emperor initially exiled him for defending the Nicene Creed, public pressure eventually forced the ruler to allow the bishop to return to his position.
Life and ministry
During his tenure, Bretannio acted as a defender of orthodox doctrine. He is associated with the transmission of the relics of Sabbas the Goth to Cappadocia, an act documented in a letter sent to the church in his region. While some historical records suggest he may have attended the Council of Constantinople in 381, scholars note his name might be confused with Gerontius, another bishop from the same see.
Veneration
He is recognized as a saint within the Catholic and Orthodox traditions. His commemoration occurs on January 25, a date that was assigned to him by the martyrologist Baronio. He remains a figure of historical importance for the early Christian communities in the region of Scythia Minor.