Martin Luther
Martin Luther was a German theologian and priest whose Ninety-Five Theses, criticizing practices of the Catholic Church, sparked the Protestant Reformation and permanently altered the course of Christianity.
Luther, an Augustinian monk and professor of theology, grew increasingly critical of the Catholic Church's sale of indulgences, payments believed to reduce punishment for sins, viewing the practice as corrupt and theologically unsound.
In 1517, he reportedly nailed his Ninety-Five Theses, outlining his objections, to the door of All Saints' Church in Wittenberg, an act that, aided by the recent invention of the printing press, spread rapidly across Europe.
Luther was excommunicated by the Pope in 1521 and went on to translate the Bible into German, making scripture more accessible, and his teachings launched the Protestant Reformation, leading to the formation of numerous Protestant denominations that continue today.