Which emperor founded Constantinople as Nova Roma in 330?

Constantine I founded Constantinople as Nova Roma in 330.

Constantine the Great transformed the old Greek city of Byzantium into a new imperial capital on the Bosporus. The site offered commanding access between Europe and Asia, the Black Sea and the Mediterranean, and the eastern provinces that were becoming increasingly important to the Roman Empire. The city was ceremonially dedicated on 11 May 330.

Its official Latin name was Nova Roma, meaning “New Rome,” but Constantinopolis, or “the city of Constantine,” quickly became the name used in common practice. Constantine expanded the settlement with monumental walls, palaces, churches, public buildings, and a major ceremonial center. He intended the city to function as a Christian and Roman imperial capital, although the older city of Rome remained symbolically important.

Constantinople became the capital of the Eastern Roman Empire after the Roman Empire was permanently divided in 395. Modern historians often call that eastern state the Byzantine Empire, but its inhabitants continued to identify themselves as Romans. Theodosius I, Arcadius, and Diocletian were important emperors, but none founded Constantinople as Nova Roma.