Martin Luther (1483-1546) was a German theologian, priest, and seminal leader of the Protestant Reformation. Initially an Augustinian monk and scholar, Luther's theological insights led him to challenge the Roman Catholic Church's practices, most notably the selling of indulgences. His 1517 publication of the "Ninety-Five Theses" sparked a movement for religious reform. Luther emphasized salvation by faith alone and the authority of the Bible over the church hierarchy, which was a shift from the prevailing Catholic teachings. His translation of the Bible into the vernacular made the scriptures more accessible to the general populace, fostering a greater literacy and understanding of Christian doctrine. Luther's ideas were instrumental in reshaping the landscape of Western Christianity and subsequently influenced the social, political, and educational spheres of the European continent.