Lothair, 941–86, French king (954–86), son and successor of King Louis IV. During the early part of his reign he was dominated by Hugh the Great. Even after Hugh's death he was involved in conflict with the great feudal lords and controlled only a small part of France. He alienated his protector, Holy Roman Emperor Otto II, by his unsuccessful attempt to occupy Lotharingia (Lorraine) in 978. Otto retaliated by invading France. Although Lothair renounced all claims to Lotharingia at a meeting with Otto in 980, he tried to regain it after Otto's death in 983. He died during the campaign and was succeeded by his son Louis V.