The famous German leader who initiated the Reformation was Martin Luther. In 1517, Luther famously wrote his "Ninety-Five Theses," challenging the practices and doctrines of the Catholic Church, particularly the sale of indulgences, which he viewed as corrupt. His actions sparked a movement that sought to reform Christianity and ultimately led to the establishment of Protestantism. Luther's insistence on justification by faith and the authority of Scripture over Church traditions resonated with many and contributed to significant theological debates throughout Europe. His ideas not only changed religious practices but also had profound social and political ramifications for centuries.