Nicholas I was a 9th-century pope who led the Papal States from 858 until his death in 867. Known as Nicholas the Great, he was a decisive figure who worked to consolidate papal authority over both religious and secular matters. He asserted that the pope held supreme jurisdiction over all Christians, including royalty, particularly regarding matters of faith and morality. His reign was marked by significant efforts to enforce ecclesiastical discipline and defend the primacy of the Roman See against various regional bishops and monarchs.