Constantine I, also known as Constantine the Great, was Roman emperor from AD 306 to 337. He was the first emperor to convert to Christianity. Born in Naissus, Dacia Mediterranea, he was the son of Flavius Constantius, a Roman army officer of Illyrian origin who had been one of the four rulers of the Tetrarchy. His mother, Helena, was a Greek woman of low birth and a Christian. Later canonized as a saint, she is traditionally attributed with the conversion of her son. Constantine served with distinction under the Roman emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces before being recalled in the west to fight alongside his father in the province of Britannia. After his father's death in 306, Constantine was acclaimed as augustus (emperor) by his army at Eboracum. He eventually emerged victorious in the civil wars against emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.