The Leipzig Debate (German: Leipziger Disputation) was a theological disputation originally between Andreas Karlstadt and Johann Eck. Eck, a staunch defender of Roman Catholic doctrine, had challenged Karlstadt to a public debate concerning the doctrines of free will and grace. The Leipzig Debate took place at Pleissenburg Castle (now the location of the city hall) in Leipzig, and lasted from June to July 1519.
Martin Luther arrived in Leipzig and joined the debate in July 1519, at the invitation of Eck. Luther and Eck expanded the terms of the debate, to include matters such as purgatory, the sale of indulgences, the need for and methods of penance, and the legitimacy of papal authority.
A joint verdict on the outcome of the debate was to be issued by the University of Erfurt and the University of Paris, but the theological faculty of Erfurt recused itself. The faculty in Paris delivered a negative verdict on Luther's writings in 1521, but made no direct reference to the debate in Leipzig itself.