The Duchy of Aquitaine was a historical fiefdom in western, central, and southern areas of present-day France to the south of the river Loire, although its extent, as well as its name, fluctuated greatly over the centuries, at times comprising much of what is now southwestern France (Gascony) and central France.

The Treaty of Verdun, agreed in August 843, divided the Frankish Empire into three kingdoms between Lothair I, Louis II and Charles II, the surviving sons of the emperor Louis I, the son and successor of Charlemagne. The treaty was concluded following almost three years of civil war and was the culmination of negotiations lasting more than a year. It was the first in a series of partitions contributing to the dissolution of the empire created by Charlemagne and has been seen as foreshadowing the formation of many of the modern countries of western Europe.