Cyriacus I of Byzantium

Cyriacus (Greek Kyriakos, sometimes called Cyrillianus ) ( † 230) was bishop of Byzantium.

The beginning of his term is usually applied to the year 217 ( according to other sources: 214) dated. According to the information provided by the bishop lists, he served 14 years under the emperors Macrinus, Elagabalus and Alexander Severus. In the office of bishop, he broke from Philadelphus; his successor was Castinus