Nicholas I, Saint, c.825–867, pope (858–67), a Roman; successor of Benedict III. He was a vigorous and politically active pope who arbitrated both temporal and religious disputes. His decisions often set important precedents, as when the pope upheld the right of the bishop of Soissons to appeal to Rome against his superior, Archbishop Hincmar. Much of his pontificate was concerned with preventing the proposed divorce of Lothair of Lotharingia, who wished to remarry. Even when Holy Roman Emperor Louis II occupied Rome, the pope refused to yield. In the end he forced Lothair to reinstate his wife. Nicholas challenged the right of Photius to occupy the see of Constantinople and attempted to have St. Ignatius of Constantinople restored to it. St. Nicholas worked with Boris I to introduce Roman ecclesiastical jurisdiction in Bulgaria, which had recently been converted by the Byzantines. A letter from the pope to Boris is extant. He was succeeded by Adrian II. Feast: Nov. 13.