The Diet of Worms was an assembly held in 1521 in the city of Worms, Germany. It was convened by the Holy Roman Emperor Charles V to address the teachings of Martin Luther, a key figure in the Protestant Reformation. Luther was summoned to defend his writings, which criticized the Catholic Church's practices, particularly the sale of indulgences. During the assembly, Luther famously refused to recant his views, stating that he could not go against his conscience. The Diet ultimately declared him an outlaw, leading to significant religious and political changes in Europe, as it fueled the spread of Protestantism.