13. The First Council of Lyons, 1245 A.D.

The First Council of Lyon (Lyon I) was the thirteenth ecumenical council, as numbered by the Catholic Church, taking place in 1245.

The First General Council of Lyon was presided over by Pope Innocent IV. Innocent IV, threatened by Holy Roman Emperor Frederick II, arrived at Lyon on 2 December 1244, and early the following year he summoned the Church's bishops to the council later that same year. Some two hundred and fifty prelates responded including the Latin Patriarchs of Constantinople, Antioch, and Aquileia (Venice) and 140 bishops. The Latin emperor Baldwin II of Constantinople, Raymond VII, Count of Toulouse, and Raymond Bérenger IV, Count of Provence were among those who participated. With Rome under siege by Emperor Frederick II, the pope used the council to excommunicate and depose the emperor with Ad Apostolicae Dignitatis Apicem, as well as the Portuguese King Sancho II. The council also directed a new crusade (the Seventh Crusade), under the command of Louis IX of France, to reconquer the Holy Land.