The Protestant Reformation was initiated by Martin Luther in the early 16th century. In 1517, Luther famously published his "Ninety-Five Theses," challenging the practices of the Catholic Church, particularly the sale of indulgences. His call for reform emphasized the importance of faith and Scripture while questioning ecclesiastical authority. Luther’s ideas quickly spread, leading to the formation of new Christian denominations and significant religious, political, and cultural shifts across Europe. The Reformation not only transformed the landscape of Christianity but also spurred the rise of individualism and modernity, reshaping the course of Western civilization.