Lothaire I, emperor of the West, born about 796, died at Prum, Sept. 29, 855. When in 817 his father Louis le Debonnaire shared the empire with his three sons, Lothaire, Pepin, and Louis, the first received the largest portion, and the right of suzerainty over his brothers. In 822 he was crowned king of Italy by the bishop of Milan, and on April 5, 823, he received the imperial crown from Pope Paschal. After the birth of Charles the Bald, and the bestow-ment upon him of a domain at the expense of his elder brothers, Lothaire excited Pepin and Louis to revolt, and twice dethroned his father, in 830 and 833. He became emperor on the death of his father in 840, but was involved in disputes with his brothers Louis and Charles, and was defeated by them in the battle of Fon-tenay, June 25, 841. By the treaty of Verdun in 843, he received Italy, Burgundy, and a district in the east of France, which was afterward (from his son Lothaire, its first king) called Lotharingia or Lorraine. During the wars of Lothaire the Normans plundered the coasts of the North sea, the Saracens devastated his Italian provinces, and the clergy and barons greatly extended their power.

After dividing his states among his three sons, the emperor became a monk in the convent of Prum, in the Ardennes highlands, and died six days after being received.