As one of the most influential and recognizable religious figures in history, Martin Luther continues to impact the world over 550 years after his death. Luther was a German priest and theologian whose writings and teachings sparked the Protestant Reformation in the early 16th century, creating one of the greatest schisms in the history of the Catholic Church and touching off religious turmoil and bloodshed that would engulf Europe for the next 2 centuries.

Born shortly after the invention of the printing press, Luther became one of Europe’s best selling authors, along with others like Erasmus, and his theology was mass produced across Europe. He strongly disputed the claim that freedom from God's punishment of sin could be purchased with money, known as indulgences, and he confronted indulgence salesman Johann Tetzel with his 95 Theses in 1517, one of the most important religious writings of all time. His refusal to retract all of his writings at the demand of Pope Leo X in 1520 and the Holy Roman Emperor Charles V at the Diet of Worms in 1521 resulted in his excommunication by the Vatican and condemnation as an outlaw by the emperor.

Luther, of course, did not back down. Although the story about him nailing 95 Theses to a church door is almost surely apocryphal, Luther continued that salvation is not earned by good deeds but received only as a free gift of God's grace through faith in Jesus Christ as redeemer from sin. His theology also continued to directly challenge the Pope’s authority by teaching that the Bible is the only source of divinely revealed knowledge.

That said, the Protestant Reformation, despite often being associated with the symbolic figure of Martin Luther nailing his 95 Theses to the door of the Castle Church in Wittenberg on October 31, 1517, cannot be reduced to a single, abrupt, and exceptional event.