The movement in Europe that sought to reform the Catholic Church and ultimately led to the establishment of Protestantism was the Reformation. Beginning in the 16th century, figures like Martin Luther, John Calvin, and Huldrych Zwingli criticized church practices, including the selling of indulgences and corruption within the clergy. The Ninety-Five Theses, posted by Luther in 1517, became a catalyst for widespread reform. The Reformation resulted in the fragmentation of Christianity, giving rise to various Protestant denominations and fostering significant religious, political, and cultural changes across Europe.