Martin Luther (1483-1546) was a German monk, priest, and theologian who is widely regarded as the father of the Protestant Reformation. Luther studied theology and law at university before entering the Augustinian monastic order. He became unsatisfied with the practices of the Roman Catholic Church, particularly the sale of indulgences. In 1517 he posted his famous "Ninety-Five Theses" on the door of the Wittenberg Castle church, which challenged the Catholic Church's authority. This is often regarded as what laid the groundwork for the Protestant Reformation which began to unfold. Luther's ideas on justification by faith, the priesthood of all believers, and the authority of scripture over tradition had a profound impact on the Church and Western civilization. He translated the Bible into German, making it accessible to the common people, and his writings and teachings helped to spread the Reformation throughout Europe. Today, Luther is remembered as one of the most influential figures in Western history and his legacy continues to shape Protestant Christianity.