Biscay, Bay of (bĭs`kā), arm of the Atlantic Ocean, indenting the coast of W Europe from Ushant island (Île d'Ouessant) off Brittany, NW France, to Cape Ortegal, NW Spain. The bay is noted for its sudden, severe storms and its strong currents. The rocky northeastern and southern coasts of Biscay are irregular with many good harbors; numerous offshore islands are there. The southeastern shore is straight and sandy. The chief ports are Brest, Saint-Nazaire, La Rochelle, and Bayonne in France and San Sebastián, Bilbao, and Santander in Spain. Nantes and Bordeaux, at the head of the Loire and Garonne estuaries, respectively, in France, are also reached by oceangoing ships. There are several resorts along the French coast, notably Biarritz. The bay has important fishing and oyster grounds.