The Bay of Biscay (Spanish: Golfo de Vizcaya and Mar Cantábrico; French: Golfe de Gascogne; Basque: Bizkaiko Golkoa; Occitan: Golf de Gasconha) is a gulf 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 west to Punta de Estaca de Bares, and is named for the Spanish province of Biscay.
The average depth is 5,723 feet (1,744 m) and maximum depth is 9,151 feet (2,789 m).
Parts of the continental shelf extend far into the bay, resulting in fairly shallow water in many areas and thus in the rough seas for which the region is known. The Bay of Biscay is home to some of the Atlantic Ocean's fiercest weather. Large storms occur in the bay, especially during the winter months. Up until recent years it was a regular occurrence for merchant vessels to founder in Biscay storms, and many lives were lost. Improved ships and weather prediction have reduced the toll of the storms.
The main rivers that end in the Bay of Biscay are:
- France: Loire, Charente, Garonne, Dordogne, Adour.
- Spain: named westward : Bidasoa, Urola , Nervión, Asón, Pas, Deva, Nalón, Navia, Eo, Landro, Sor.
The main cities on the shores of the Bay of Biscay are:
- France: Brest, Nantes, La Rochelle, Bordeaux, Bayonne.
- Spain: San Sebastian, Bilbao, Santander, Gijon.
The southern end of the gulf is also called in Spanish "Mar Cantábrico" (Cantabrian Sea), for the region of Cantabria, but this name is not generally used in English. It was named by Romans in 1st century BC as Sinus Cantabrorum (Bay of the Cantabri).
On some medieval maps, the Bay of Biscay is marked as El Mar del los Vascos, the Basque Sea. The Bay of Biscay is the birthplace of what is considered one of the world's most successful and most renowned maritime industries, the Basque and Cantabrian shipbuilders and fishermen.
The car ferries from Portsmouth to Bilbao and from Plymouth, Portsmouth and Poole to Santander provide one of the most convenient ways to see cetaceans in European waters, and there are often specialist trips on board.
Volunteers and employees from the Biscay Dolphin Research Programme use the bridge of the vessel on the P&O Portsmouth to Bilbao run to observe and monitor cetacean activity. Many species of whales and dolphins can be seen in this area but it is one of the few places where the beaked whales such as the Cuvier's beaked whale have been observed relatively frequently. This is the best study area for beaked whales in the world.
The alga Colpomenia peregrina was introduced and first noticed by oyster fishermen in the Bay of Biscay in 1906.