The First Council of Lyon, convened by Pope Innocent IV in 1245, was the thirteenth ecumenical council of the Catholic Church. It was held at Lyon because the pope had fled Rome to escape the hostility of Holy Roman Emperor Frederick II. The council formally excommunicated Frederick II, deposing him and declaring him a tyrant. It also addressed various ecclesiastical reforms and crusading efforts, marking a significant moment in the ongoing conflict between the papacy and the empire.

The council's decree of deposition against Frederick II was a major political and religious event that was widely discussed in contemporary chronicles and polemical literature. The pope's actions and the emperor's defiance inspired a range of works, including satirical poems and propagandistic tracts. This conflict between spiritual and temporal authority became a recurring theme in medieval literature, as exemplified by the writings of Joachim of Fiore and other apocalyptic thinkers.