AUNIS was formerly a province (pays) of France, bounded on the north by Poitou, on the west by the Atlantic, and on the south and east by Saintonge. Its principal town was at first Chatelaillon, and later La Rochelle ; the latter city was founded in 1117 by Duke Guillaume X. of Aquitaine. Other towns are Saujon and St. Jean d'Angely. Aunis formed part of the diocese of Saintes until 1648. In that year it was joined to the former diocese of Maillezais (created in 1317), and the bishop's see was transferred to La Rochelle. For the administration of justice, Aunis came under the Parlement of Paris; it was subject to the jurisdiction of the presidial of La Rochelle. For military pur poses, Aunis constituted a separate Government (gouvernement general) which included the islands of Re and Oleron and had its headquarters at La Rochelle.
Aunis (pagus Alnensis) possibly derives its name from its old capital Chatelaillon (castrum qui vocatur Allionis) . It very early became a feudal dependence of Poitou, and shared the political fortunes of that province. It now forms the north western part of the department of Charente-Inferieure.