Carolingian king of France from 954 to 986, the eldest son of Louis IV. He was elected king without opposition after his father's death but was dominated first by Hugh the Great and then, from 956 to 965, by his uncle, Bruno (Bruno the Great, Saint), archbishop of Cologne, whose support was invaluable but who used his influence also in the interests of Otto I, his brother, the German king, and of Hugh Capet and the other sons of Hugh the Great, Bruno's nephews.

After Bruno's death, Lothar's position deteriorated. Although his relations with Hugh Capet were generally good, he had only a tiny domain and was much distracted by feudal conflict. Also, a persistent desire to get Lorraine from the German allegiance brought negative consequences: his support of a revolt there (976) against Otto II impelled the latter to give the duchy of Lower Lorraine to Lothar's refractory brother, Charles; Lothar's plan to capture Otto's family at Aachen (978) miscarried and provoked a retaliatory attack on France, which Lothar, with the support of the aristocracy and especially Hugh Capet, was able to repel; and a third invasion of Lorraine (985) not only failed in its purpose but determined the powerful Archbishop Adalbero of Reims to support Hugh Capet against Lothar. Lothar was, however, preparing yet another expedition into Lorraine when he died, to be succeeded by his son, Louis V.

king of Italy in the chaotic post-Carolingian period. He was named after his great-grandfather Lothar II and ruled as co-king with his father, Hugh of Provence, from 931 until Hugh's exile and death in 947. Lothar remained in Italy when his father, harassed by the powerful Lombard Berengar II of Ivrea, fled to Provence. Marrying 16-year-old Adelaide, daughter of Rudolf II of Burgundy (later wife of Emperor Otto I), in the hope of strengthening his position, Lothar found himself playing the role of a figurehead, while Berengar exercised the real power in Italy. Lothar died in 950, possibly poisoned by Berengar, who succeeded him. The succession elicited the intervention in Italy of King Otto I, the future Holy Roman emperor.