Luther's efforts to reform the theology and practice of the Catholic Church launched the Protestant Reformation in the German-speaking territories of the Holy Roman Empire. Beginning with the Ninety-Five Theses, first published in 1517, Luther's writings were disseminated internationally, spreading the early ideas of the Reformation beyond the influence and control of the Roman Curia and the Holy Roman Emperor. The split between the Lutherans and the Catholics was made public and clear with the 1521 Edict of Worms: the edicts of the Diet condemned Luther and officially banned citizens of the Holy Roman Empire from defending or propagating his ideas, subjecting advocates of Lutheranism to forfeiture of all property, half of the seized property to be forfeit to the imperial government and the remaining half forfeit to the party who brought the accusation. The divide centered primarily on two points: the proper source of authority in the church, often called the formal principle of the Reformation, and the doctrine of justification, often called the material principle.
Lutheranism advocates a doctrine of justification "by grace alone through faith alone on the basis of Scripture alone", the doctrine that scripture is the final authority on all matters of faith. This is in contrast to the belief of the Catholic Church, defined at the Council of Trent, concerning authority coming from both the Scriptures and Tradition. In addition, Lutheranism accepts the teachings of the first seven ecumenical councils of the Christian Church. The Augsburg Confession, a Lutheran statement of belief contained in the Book of Concord, teaches that "the faith as confessed by Luther and his followers is nothing new, but the true catholic faith, and that their churches represent the true catholic or universal church". When the Lutherans presented the Augsburg Confession to Charles V, Holy Roman Emperor, they believe to have "showed that each article of faith and practice was true first of all to Holy Scripture, and then also to the teaching of the church fathers and the councils".
Unlike Calvinism, Lutherans retain many of the liturgical practices and sacramental teachings of the pre-Reformation Church, with a particular emphasis on the Eucharist, or Lord's Supper. Lutheran theology differs from Reformed theology in Christology, the purpose of God's Law, the divine grace, the concept of perseverance of the saints, and predestination.
Today, Lutheranism is one of the largest denominations of Protestantism. With approximately 80 million adherents, it constitutes the third most common Protestant denomination after historically Pentecostal denominations and Anglicanism. The Lutheran World Federation, the largest communion of Lutheran churches, represents over 74 million people. Other Lutheran organizations include the International Lutheran Council and the Confessional Evangelical Lutheran Conference, as well as independent churches.
The name Lutheran originated as a derogatory term used against Luther by German Scholastic theologian Dr. Johann Maier von Eck during the Leipzig Debate in July 1519. Eck and other Catholics followed the traditional practice of naming a heresy after its leader, thus labeling all who identified with the theology of Martin Luther as Lutherans.