John Calvin was a French theologian, pastor, and reformer who became a central figure in the Protestant Reformation. Born in Noyon around 1509, he was originally trained in law before his religious conversion led him to break from the Roman Catholic Church. He spent much of his career in Geneva, where he helped shape the city's religious and political life. His theological work established the foundations of Calvinism, a system of Christian belief that emphasizes the absolute sovereignty of God and the doctrine of predestination.