Agenais, or Agenois, a former province of France.

In ancient Gaul it was the country of the Nitiobroges with Aginnum for its capital, and in the 4th century it was the Cimtas Agennensium which was a part of Aquitania Secunda and which formed the diocese of Agen. Having in general shared the fortunes of Aquitaine during the Merovingian and Carolingian periods, Agenais next became an hereditary countship in the part of the country now called Gascony (Vasconia).

In 1038 this countship was purchased by the dukes of Aquitaine and counts of Poitiers. The marriage of Eleanor of Aquitaine with Henry Plantagenet in 1152 brought it under the sway of England; but when Richard Coeur-de-Lion married his sister Joan to Raymund VI, Count of Toulouse, in 1196, Agenais formed part of the princess's dowry; and with the other estates of the last independent count of Toulouse it lapsed to the crown of France in 1271.

This, however, was not for long; the king of France had to recognize the prior rights of the king of England to the possession of the countship, and restored it to him in 1279. During the wars between the English and the French in the 14th and 15th centuries, Agenais was frequently taken and retaken, the final retreat of the English in 1453 at last leaving the king of France in peaceable possession. Thenceforth Agenais was no more than an administrative term. At the end of ancien regime it formed part of the "Gouvernement" of Guienne, and at the Revolution it was incorporated in the department of Lot-et-Garonne, of which it constitutes nearly the whole. The title of count of Agenais , which the kings of England had allowed to fall into desuetude, was revived by the kings of France, and in 1789 was held by the family of the dukes of Richelieu.

There is no good history of Agenais; that published by Jules Andrieu in 1893 (Histoire de l'Agenais, 2 vols.) being quite inadequate. The Bibliographie generate de I' Agenais, by the same author (1886-1891, 3 vols.), may be found useful.