(ăk'wĭtān, äkētĕn'), Lat. Aquitania, former duchy and kingdom in SW France. Julius Caesar conquered the Aquitani, an Iberian people of SW Gaul, in 56 B.C. The province that he created occupied the territory between the Garonne River and the Pyrenees; under Roman rule it was extended northward and eastward almost as far as the Loire River. It had been thoroughly Romanized when it was occupied (5th cent.) by the Visigoths, and the persistence of Latin culture made it a rich but indigestible addition to the Frankish realm after the defeat (507) of the Visigoths by the Frankish ruler Clovis I. In the chaotic strife among Clovis's successors, much of Aquitaine escaped Frankish control. After the separation of Gascony from Aquitaine (7th cent.), the area N of the Garonne was considered Aquitaine proper.
From 670, Aquitaine was ruled by semi-independent native dukes, but an Arab invasion (718) forced the Aquitanian duke Eudes to seek the protection of the Frankish ruler Charles Martel, who defeated (732) the Arabs. In 781, Charlemagne, who subdued the native nobles, made Aquitaine into a kingdom for his son Louis (later emperor of the West Louis I). After the death (838) of Louis's son Pepin I, Louis added Aquitaine to the West Frankish kingdom of Neustria (France) and granted it to his youngest son Charles the Bald (Charles II, emperor of the West). A group of Aquitanian nobles made Pepin's young son, Pepin II, king, and a struggle for control ensued between Charles and the Aquitanians (840–52; 862–65). Charles was the eventual victor. During this period Aquitaine was subject to attacks by both Normans and Muslims. The repeated invasions, combined with the civil wars, weakened Carolingian control over Aquitaine, despite Charles the Bald's victory over Pepin II. Charles's successors were forced to recognize the hereditary rights of a number of independent noble families, and during the 10th cent. royal influence virtually disappeared.
After 973 the counts of Poitou bore the title of duke of Aquitaine; their control beyond Poitou, however, was not realized for many years. In the 11th cent. the dukes of Aquitaine expanded at the expense of their weaker neighbors, establishing themselves over all Aquitaine and Gascony. The new duchy of Aquitaine was one of the most powerful states in western Europe. The marriage (1137) of Eleanor of Aquitaine to French king Louis VII joined Aquitaine to France. Eleanor's subsequent marriage to Henry II, duke of Normandy, who became king of England in 1154, initiated a long struggle between France and England for possession of Aquitaine. Henry and his successors held Aquitaine in vassalage from the kings of France. Over the years, however, France regained various parts of Aquitaine from England, and in the Hundred Years War France recovered all of Aquitaine. After its recovery, Aquitaine was constituted as the French province of Guienne, a name that had been used interchangeably with Aquitaine for many years.