Not to be confused with the North American Biscayne Bay.

The Bay of Biscay (French: Golfe de Gascogne; Spanish: Mar Cantábrico) is an arm of the North Atlantic Ocean. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain. Large parts of the bay are shallow water lying above the continental shelf.

The car ferries from Portsmouth to Bilbao and from Plymouth to Santander provide one of the most convenient ways to see cetaceans in European waters, and there are often specialist trips on board. The best areas are those over deep water once the continental shelf has been left behind. The three-day round trip also gives sightings of good numbers of several species of seabirds.