Kyrillos I was a 3rd-century bishop of Antioch who served as the successor to Timaios. He led the local Christian community during a period of significant political transition in the Roman Empire. Although the era was marked by the intense persecutions initiated by Emperor Diocletian, Kyrillos appears to have passed away peacefully, potentially before these widespread religious crackdowns began. He was succeeded in his episcopal role by Tyrannion.