The Protestant Reformation was a movement of spiritual and ecclesial renewal that took place among Christians in the West during the sixteenth century. The Reformation was also a revolution in the original sense of that word: the return of an object to its point of origin. Ad fontes!—back to the sources—was common to the Reformation in all of its major expressions. Both the unity and the diversity of the Reformation as a movement of renewal are best seen through the personal stories of those who led the movement. In this lecture series, we focus on four major characters, each with a legacy that continues to shape the heritage of the Reformation 500 years after the event: Desiderius Erasmus, Martin Luther, John Calvin, and William Tyndale.