GEX, a town of eastern France, chief town of an arrondissement in the department of Ain, 10 m. N.W. of Geneva and 3 m. from the Swiss frontier. Pop. (1906) town, 1385; commune, 2727. The town is beautifully situated 2000 ft. above sea-level at the base of the most easterly and highest chain of the Jura. It is the seat of a subprefect and has a tribunal of first instance, and carries on considerable trade in wine, cheese and other provisions, chiefly with Geneva. It gives its name to the old Pays de Gex, situated between the Alps and the Jura, which was at various times under the protection of the Swiss, the Genevese and the counts of Savoy, until in 1601 it came into the possession of France, retaining, however, until the Revolution its old independent jurisdiction, with Gex as its chief town. The Pays de Gex is isolated by the Jura from the rest of French territory, and comes within the circumscription of the Swiss customs, certain restrictions being imposed on its products by the French customs.