Louis I or Louis the Pious, Fr. Louis le Pieux or Louis le Débonnaire, 778–840, emperor of the West (814–40), son and successor of Charlemagne. He was crowned king of Aquitaine in 781 and co-emperor with his father in 813. His court was a learned one; his advisers included Benedict of Aniane. At the Assembly of Aachen (817) he issued an imperial order that sought to preserve the unity of the empire by breaking with tradition and not dividing the empire among his heirs. He thus made his eldest son, Lothair I, co-emperor and gave Aquitaine and Bavaria to his sons Pepin I and Louis the German. Louis's attempts to create a kingdom for Charles (later Emperor of the West Charles II), his son by a second marriage, provoked several revolts by his older sons. In 822, Louis repented publicly for his persecution of the rebels. In 830, Lothair rebelled and became virtually sole ruler of the empire. However, Pepin and Louis the German, fearing Lothair's supremacy, soon restored their father to power. Another revolt by all three sons occurred in 833. Louis met the rebels near Colmar on a field known since then as the Field of Lies (Ger. Lügenfeld ) because of the general defection of the imperial troops. Louis, compelled to surrender, was formally deposed, and Lothair became sole emperor. Yet in 834, Louis the German and Pepin once more joined against Lothair and restored Louis. Later he partitioned his empire between Lothair and Charles and died while attempting to uphold the partition against the Aquitanians and Louis the German.
See F. L. Ganshof, The Carolingians and the Frankish Monarchy (1971).