The event that marked the beginning of the Protestant Reformation in 1517 was Martin Luther’s publication of his Ninety-Five Theses. Luther, a German monk and theologian, criticized the Catholic Church's practices, especially the sale of indulgences, which he believed undermined genuine faith and salvation. His theses challenged the Church's authority and sparked widespread debate across Europe. The document was circulated widely, facilitated by the invention of the printing press, and resonated with many, leading to the emergence of various Protestant denominations. This movement deviated from Catholic traditions and ultimately resulted in significant religious, political, and social changes, transforming the landscape of Christianity.