Martin Luther (1483-1546)German leader of the Protestant Reformation, b. Eisleben, Saxony, of a family of small, but free, landholders. Sixteenth-century leader of the Protestant Reformation, Martin Luther was a German monk who began to preach against the Catholic Church’s doctrines and practices, especially the legitimacy of indulgences, the Mass as a representation of Christ’s sacrifice, and vows of celibacy required for priests. Martin Luther initiated a movement of criticism that extended beyond the scope of his own reform efforts, especially during the Enlightenment.