Constantine the Great

Roman emperor who transformed Christianity from a persecuted minority faith into the dominant religion of the Western world. After his vision at the Battle of Milvian Bridge in 312 AD, Constantine defeated his rival Maxentius and became sole emperor of the West. The following year he issued the Edict of Milan, legalizing Christianity throughout the Roman Empire. In 325 AD he convened the Council of Nicaea — the first ecumenical council — where bishops from across the empire defined core Christian doctrine including the Nicene Creed. He moved the imperial capital to Byzantium (renamed Constantinople), which became the center of Eastern Christianity for over a thousand years. Whether his conversion was genuine personal faith or political calculation remains one of history's great debates — but its impact on the Church is undeniable.