Aquitaine (Occitan: Aquitània; Basque: Akitania; Spanish: Aquitania), archaic Guyenne/Guienne (Occitan: Guiana), is one of the 27 Regions of France, in the south-western part of Metropolitan France, along the Atlantic Ocean and the Pyrenees mountain range on the border with Spain. It is composed of the 5 departments of Dordogne, Lot et Garonne, Pyrénées-Atlantiques, Landes and Gironde. In the Middle Ages Aquitaine was a kingdom and a duchy, whose boundaries fluctuated considerably.

After the 843 Treaty of Verdun, the defeat of Pepin II and the death of Charles the Bald, the Kingdom of Aquitaine (subsumed in West Francia) ceased to have any relevance and the title of King of Aquitaine took on a nominal value. In 1058, the Duchy of Vasconia (Gascony) and Aquitaine merged under the rule of William VIII, Duke of Aquitaine.

The title "Duke of Aquitaine" was held by the counts of Poitiers from the 10th to the 12th century.

It passed to France in 1137 when the duchess Eleanor of Aquitaine married Louis VII of France, but their marriage was annulled in 1152 and when Eleanor's new husband became Henry II of Englandin 1154, the area became an English possession. They where the parents of Richard the Lionheart and John Lack-land.

Links between Aquitaine and England were strengthened, with large quantities of wine produced in southwestern France being exported to London, Southampton, and other English ports.

Aquitaine remained English until the end of the Hundred Years' War in 1453, when it was annexed by France. From the 13th century until the French Revolution, Aquitaine was usually known as Guyenne.

The region served as a stronghold for the Protestant Huguenots during the sixteenth and seventeenth centuries, who suffered persecution at the hands of the Roman Catholic Church. The Huguenots called upon the English crown for assistance against the barbaric Catholic Cardinal Richelieu who inspired many bloody inquisitions against anyone who dared to disagree with his own beliefs.