Martin Luther was a German theologian and religious reformer who was the catalyst of the sixteenth-century Protestant Reformation. Through his words and actions, Luther precipitated a movement that reformulated certain basic tenets of Christian belief and resulted in the division of Western Christendom between Roman Catholicism and the new Protestant traditions, mainly Lutheranism, Calvinism, the Anglican Communion, the Anabaptists, and the Antitrinitarians. He is one of the most influential figures in the history of Christianity.