Martin Luther was a German priest in the early 16th century who sparked the Protestant Reformation. Originally training to be a lawyer, Luther became dissatisfied with the Catholic Church's teachings and practices. He wrote his famous 95 Theses criticizing the Church's sale of indulgences and doctrine of salvation through faith and works. This led Luther to be excommunicated by the Pope and declared an outlaw by the Holy Roman Emperor, though his ideas had already spread widely. Luther's actions inspired Protestants across Europe to break away from Catholicism and form new denominations.