Constantine I, also known as Constantine the Great, ruled the expanding Roman Empire from 306 until his death in 337. As a result of his victory in 312 at the Battle of Milvian Bridge, he became ruler of the entire western half of the empire. He gradually consolidated his military power over his rivals and became emperor over all of Rome.
During his reign, Constantine passed laws regarding farmers that laid the foundation for medieval European society. But Constantine's most important accomplishment was making Christianity the unofficially sponsored religion of Rome, which was a major factor in the spread and acceptance of the religion. Until Constantine's actions, early Christians had suffered terrible persecution.
The city of Constantinople, which gradually became the capital of the Roman Empire, was named after him.