OLÉRON, an island lying off the west coast of France, opposite the mouths of the Charente and Seudre, and included in the department of Charente-Inférieure. In 1906 the population numbered 16,747. In area (66 sq. m.) it ranks next to Corsica among French islands. It is about 18 m. in length from N.W. to S.E., and 7 in extreme breadth; the width of the strait (Pertuis de Maumusson) separating it from the mainland is at one point less than a mile. The island is flat and low-lying and fringed by dunes on the coast. The greater part is very fertile, but there are also some extensive salt marshes, and oyster culture and fishing are carried on. The chief products are corn, wine, fruit and vegetables. The inhabitants are mostly Protestants and make excellent sailors. The chief places are St Pierre (pop. 1582 in 1906), Le Château d'Oléron (1546), and the watering-place of St Trojan-les-Bains.
Oléron, the Uliarus Insula of Pliny, formed part of the duchy of Aquitaine, and finally came into the possession of the French crown in 1370. It gave its name to a medieval code of maritime laws promulgated by Eleanor of Guienne.