Marcus I of Byzantium

Marcus I. (Greek: Markos ) ( † 211) was bishop of Byzantium. His tenure has been dated to the years 198-211, and thus falls within the reign of the Emperor Septimius Severus. This had not only taken the city because of their opposition against him in the second year of four emperors their liberties, but he also undertook long-lasting persecution of Christians. Therefore, it is not clear whether Marcus could actually exercise the episcopal office for the entire 13 years, or whether he had to leave it because of the persecution to a deputy.

His successor was Philadelphus.