Castinus of Byzantium

Castinus' (Greek Μάρκος Α') was Bishop of Byzantium from 230 until 237 AD.

Castinus was born in Rome to a noble family and was originally a pagan. He was converted to Christianity by the Bishop of Argyroupolis Kastillianos.

Castinus gave away his earthly possessions to the poor and fully dedicated himself to the Church.

During his tenure as Bishop of Byzantium, he built the first cathedral - Saint Euphemia - within Byzantium. Up until that time, the cathedral was situated in Galata.