Verdun, Treaty of, 843, an agreement by which the three sons of Emperor Louis I, the Pious, divided the empire built by Charlemagne. Louis, the son of Charlemagne, had made several unsuccessful attempts to divide his empire to the satisfaction of his sons. After his death in 840, civil war broke out among the sons. Finally at Verdun, 140 miles (225 km) east-northeast of Paris, the brothers agreed on a division that set up three kingdoms of about equal size.

Charles the Bald received the Kingdom of the West Franks. Louis the German obtained the Kingdom of the East Franks. Lothair, the oldest, was recognized as emperor and received the middle territory, which extended from the Low Countries through northern Italy. The West Frankish kingdom developed eventually into France and the East Frankish kingdom into Germany. Lothair's kingdom soon broke up into separate autonomous states, such as Burgundy, Alsace, Lorraine, and the Flemish counties and towns.