LOTHAIR I., Roman emperor, eldest son of Louis the Pious, was born in 795. At a diet held at Aix-la-Chapelle in 817 he received Austrasia with the greater part of Germany, and was associated with his father in the empire, while separate territories were granted to his brothers Louis and Pippin. This arrangement being modified in favour of Louis’s youngest son Charles (afterwards Charles the Bald), the three brothers repeatedly rebelled, and for a time Lothair usurped supreme power. After the death of Louis in 840, Lothair, as his successor, claimed the right to govern the whole empire. His brothers Louis and Charles (Pippin being dead) united against him, and in 841 he was defeated in the great battle of Fontenay. On the 11th of August 843 the war was brought to an end by the treaty of Verdun, by which Lothair was confirmed in the imperial title, but received as his immediate territory only Italy (which he had ruled from 822) with a long narrow district reaching past the Rhone and the Rhine to the North Sea. His subsequent reign was full of trouble, for many of his vassals had become virtually independent, and he was unable to contend successfully with the Norsemen and the Saracens. In 855, weary of the cares of government, he divided his kingdom among his sons, and retired to the monastery of Prüm, where he died on the 28th of September of the same year. As emperor he was succeeded by his son Louis II.