Document written by Martin Luther detailing what he believed to be the problems in the mediaeval Church.

Luther's action was in great part a response to the selling of indulgences by Johann Tetzel, a Dominican priest, commissioned by the Archbishop of Mainz and Pope Leo X. The purpose of this fundraising campaign was to finance the building of St. Peter's Basilica in Rome. Even though Luther's prince, Frederick the Wise, and the prince of the neighbouring territory, Duke George of Saxony, forbade the sale in their lands, Luther's parishioners travelled to purchase them. When these people came to confession, they presented the indulgence, claiming they no longer had to repent of their sins, since the document forgave all their sins.

Traditionally, Luther posted the 95 Theses on the door of the Castle Church in Wittenberg, Germany, on October 31, 1517.