Nicholas I, or Nicholas the Great (c. 820 - November 13, 867) was a Pope who reigned from April 24, 858 until his death. He is remembered as a consolidator of Papal authority and power. He refused to grant an annulment to Lothar II from Theutberga so that Lothar could marry his mistress Waldrada; when a Council pronounced in favor of annulment, Nicholas I declared the Council to be deposed, its messengers excommunicated, and its decisions void. Despite pressure from the Carolingians, who laid siege to Rome, his decision held. During his reign, relations with the Byzantine Empire soured over his support for Ignatius as Patriarch of Constantinople, who had been removed and Photius appointed to replace him.
