Emperor Constantine I

Emperor Constantine I, also known as Constantine the Great, was the first Roman emperor to embrace Christianity, significantly shaping its role in the Roman Empire. Reigning from 306 to 337 AD, he convened the First Council of Nicaea in 325 AD, which established key Christian doctrines. He also founded Constantinople (modern Istanbul), transforming it into a major cultural and political center, and making it the new capital of the Roman Empire. His policies helped spread Christianity and altered the religious landscape of the empire, leading to its eventual dominance in Europe.