Constantine I (27 February 272 – 22 May 337 AD) was a Roman emperor from 306 until he died. He was emperor for longer than any other emperor since Augustus, the first emperor. He was the first ruler of the Roman Empire to be a Christian. He made the old city Byzantium into a new, larger city: Constantinople (now Istanbul, Turkey). The city's name means "City of Constantine" in Greek. He was the son of the emperor Constantius I, and members of their Constantinian dynasty controlled the empire until 364.