LOUIS I. (7;78-840), surnamed the "Pious," Roman emperor, third son of the emperor Charlemagne and his wife Hildegarde, was born at Chasseneuil in central France, and crowned king of Aquitaine in 781. His tastes were ecclesiastical rather than mili tary, the government of his kingdom was mainly conducted by his counsellors. In 794 or 795 he married Irmengarde, daughter of Ingram, count of Haspen. After the deaths of his two elder brothers, Louis, at his father's command, crowned himself co emperor at Aix-la-Chapelle on Sept. II, 813, and became sole ruler in the following January. He earned the surname of "Pious" by banishing his sisters and others of immoral life from court ; by attempting to reform and purify monastic life ; and by showing great liberality to the church.
In Oct. 816 he was crowned emperor at Reims by Pope Stephen IV. ; and at Aix in July 817, he arranged for a division of his empire among his sons. This was followed by a revolt of his nephew, Bernard, king of Italy; but the rising was easily suppressed, and Bernard was killed, although in 818 Louis par doned the followers of Bernard and restored their estates. In 819 he married Judith, daughter of Welf I., count of Bavaria, who in 823 bore him a son Charles, afterwards called the Bald. With the support of Judith's eldest step-son Lothair, a district was carved out for Charles in 829. Discontent at this arrangement led to a rebellion in the following year, provoked by Judith's intrigues with her favourite Bernard, count of Barcelona. Lothair and his brother Pippin joined the rebels, and after Judith had been sent into a convent and Bernard had fled to Spain, an assembly was held at Compiegne, when Louis was practically deposed and Lothair became the real ruler of the Empire. But at a second assembly held at Nimwegen in Oct. 83o he was restored to power.
Further trouble between Pippin and his father led to the nominal transfer of Aquitaine from Pippin to his brother Charles in 831. The emperor's plans for a division of his dominions then led to a revolt of his three sons. Louis met them in June 833 near Kolmar, but owing possibly to the influence of Pope Gregory IV., who took part in the negotiations, he found himself deserted
by his supporters, and the treachery and falsehood which marked the proceedings gave to the place the name of Lfigenfeld, or the "field of lies." Judith, charged with infidelity, was again banished; Louis was sent into the monastery of St. Medard at Soissons ; and the government of the empire was assumed by his sons. But when the younger Louis had failed to induce Lothair to treat the emperor in a more becoming fashion, he and Pippin took up arms on behalf of their father. The result was that in March 834 Louis was restored to power at St. Denis; Judith returned and the king doms of Louis and Pippin were increased. The struggle with Lothair continued until the autumn, when he submitted to the emperor and was confined to Italy. An assembly at Diedenhofen declared the deposition of Louis to have been contrary to law, and a few days later he was publicly restored in the cathedral of Metz. In Dec. 838 Pippin died, and the Empire, except Bavaria, the kingdom of Louis, was now divided between Lothair, recon ciled to his father, and Charles. The emperor was returning from suppressing a revolt on the part of his son Louis, when he died on June 20, 840 on an island in the Rhine near Ingelheim. He was buried in the church of St. Arnulf at Metz. Louis, who is also called Le Debonnaire, counts as Louis I., king of France.
See Annales Fuldenses; Annales Bertiniani; Thegan, Vita Hludowici; the Vita Hludowici attributed to Astronomus; Ermoldus Nigellus, In honorem Hludowici imperatoris; Nithard, Historiarum libel, all in the Monumenta Germaniae historica. Scriptores, Bande i. and ii. (Hanover and Berlin, 1826 fol.) ; E. Milhlbacher, Die Regesten des Kaiserreichs unter den Karolingern (Innsbruck, 1880 ; • and Deutsche Geschichte unter den Karolingern (Stuttgart, 1886) ; B. Simson, Jahrbiicher des friinkischen Reichs unter Ludwig dem Frommen (Leipzig, 1874-76) ; and E. Diimmler, Geschichte des ostfrankischen Reiches (Leipzig, 1887-88).