A Mighty Fortress Is Our God by Martin Luther

Martin Luther (; German: [ˈmaʁtiːn ˈlʊtɐ] ; 10 November 1483– 18 February 1546) was a German priest, theologian, author, hymnwriter, professor, and Augustinian friar. Luther was the seminal figure of the Protestant Reformation, and his theological beliefs form the basis of Lutheranism. He is widely regarded as one of the most influential figures in Western and Christian history.

Luther was ordained to the priesthood in 1507. He came to reject several teachings and practices of the Roman Catholic Church; in particular, he disputed the view on indulgences. Luther attempted to resolve these differences amicably, first proposing an academic discussion of the practice and efficacy of indulgences in Ninety-five Theses, which he authored in 1517. In 1520, Pope Leo X demanded that Luther renounce all of his writings, and when Luther refused to do so, excommunicated him in January 1521. Later that year, Holy Roman Emperor Charles V condemned Luther as an outlaw at the Diet of Worms. When Luther died in 1546, Pope Leo X's excommunication was still in effect.

Luther taught that salvation and, consequently, eternal life are not earned by good deeds; rather, they are received only as the free gift of God's grace through the believer's faith in Jesus Christ, who is the sole redeemer from sin. Luther's theology challenged the authority and office of the pope by teaching that the Bible is the only source of divinely revealed knowledge, and opposed sacerdotalism by considering all baptized Christians to be a holy priesthood. Those who identify Luther's wider teachings are called Lutherans, though Luther opposed the name, believing that those who professed faith in Christ should be called "Christian" or "Evangelic".

Luther's translation of the Bible into German from Latin made the Bible vastly more accessible to the laity, which had a tremendous impact on both the church and German culture. It fostered the development of a standard version of the German language, added several principles to the art of translation, and influenced the writing of an English translation, the Tyndale Bible. His hymns influenced the development of singing in Protestant churches. His marriage to Katharina von Bora, a former nun, set a model for the practice of clerical marriage, allowing Protestant clergy to marry.

In two later works, Luther expressed anti-Judaistic views, calling for the expulsion of Jews and the burning of synagogues. These works also targeted Roman Catholics, Anabaptists, and nontrinitarian Christians. Based upon his teachings, despite the fact that Luther did not advocate the murdering of Jews, some historians contend that his rhetoric contributed to the development of antisemitism in Germany and the emergence, centuries later, of the Nazi Party.