Martin Luther (1483–1546) was a German theologian, priest, and reformer whose 1517 Ninety-Five Theses challenging the sale of indulgences ignited the Protestant Reformation. A former Augustinian monk and professor of biblical studies at the University of Wittenberg, Luther argued that salvation comes through faith alone (sola fide) and that Scripture, not church tradition, is the final authority for Christian belief (sola scriptura). Excommunicated by the Catholic Church in 1521, he spent his later years translating the Bible into German, writing hymns and catechisms, and shaping the theology of what became the Lutheran tradition.
