Oleron, an island off the S.W. coast of France, separated from the mainland by the Passe de Maumusson, and opposite the mouth of the river Charente. It is 20 miles long and about 5 miles broad, with an area of 59 square miles. The soil is very fertile, and supports a large population, mostly Protestant. Ship-building is carried on here, and there are large salt-works. The two principal towns are Chateau d'Oleron on the S.E. coast, and St.
Pierre d'Oleron in the centre. A famous code of maritime law took its name and origin hence.