The Bay of Biscay (ˈbɪskeɪ,_ˈbɪski ), known in Spain as the Gulf of Biscay (Golfo de Vizcaya; Bizkaiko Golkoa), and in France and some border regions as the Gulf of Gascony (Golfe de Gascogne; Golf de Gasconha; Pleg-mor Gwaskogn), is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward to Cape Ortegal. The southern area of the Bay of Biscay that washes over the northern coast of Spain is known locally as the Cantabrian Sea.
The average depth is and the greatest depth is .
The Bay of Biscay is named (for English speakers) after Biscay on the northern Spanish coast, probably standing for the western Basque districts (Biscay up to the early 19th century). Its name in other languages is:
Mar Cantábricu
Bizkaiko golkoa
pleg-mor Gwaskogn
golfe de Gascogne (named after Gascony, France)
golfo de Biscaia
golf de Gasconha
Sinus Biscaiensis ( Cantabricus, Cantabrorum, Gallaecum)
Golfo de Vizcaya (mar Cantábrico for the ocean area closer to the Spanish coast, the Cantabrian Sea)
Bá na Bioscáine
Golf van Biskaje
Parts of the continental shelf extend far into the bay, resulting in fairly shallow waters in many areas and thus the rough seas for which the region is known. Heavy storms occur in the bay, especially during the winter months. The Bay of Biscay is home to some of the Atlantic Ocean's fiercest weather; abnormally high waves occur there. Up until recent years it was a regular occurrence for merchant vessels to founder in Biscay storms.
The International Hydrographic Organization defines the limits of the Bay of Biscay as "a line joining Cap Ortegal () to Penmarch Point ()".
The southernmost portion is the Cantabrian Sea.
The main rivers that empty into the Bay of Biscay are Loire, Charente, Garonne, Dordogne, Adour, Nivelle, Bidasoa, Oiartzun, Urumea, Oria, Urola, Deba, Artibai, Lea, Oka, Nervión, Agüera, Asón, Miera, Pas, Saja, Nansa, Deva, Sella, Nalón, Navia, Esva, Eo, Landro and Sor.