Olympianus (Greek: Ολυμπιανός, died 198) was the bishop of Byzantium for eleven years (187-198 A.D). He succeeded Bishop Pertinax. In 196 Byzantium was conquered by Emperor Septimus Severus during his rivalry with Pescennius Niger. Septimus Severus took the right of metropolis from the city and made it part of the Thracian Heracleia. Byzantium remained a bishopric under Heracleia for more than a century. Olympianus' successor was Marcus I.