Biscay (in Basque and officially Bizkaia and in Spanish Vizcaya) is a province of Spain located just south of the Bay of Biscay. The name also refers to a historical territory of the Basque Country, heir of the ancient Lordship of Biscay. Its capital city is Bilbao. It is one of the most prosperous and important provinces of Spain as a result of the massive industrialization in the last years of the 19th century and first half of the 20th century. Since the deep deindustrialization of the 1970s, the economy has come to rely more on the services sector.

It is accepted in linguistics (Koldo Mitxelena, etc.) that Bizkaia is a cognate of bizkar (cf. Biscarrosse in Aquitaine), with both place-name variants well attested in the whole Basque Country and out meaning 'low ridge' or 'prominence' (Iheldo bizchaya attested in 1141 for the Monte Igueldo in San Sebastián).

“Bizkaia” is the Basque denomination recommended by the Royal Academy of the Basque language, and it is commonly used on official documents on that language. It is also used on documents in Spanish, and it is the most used denomination by the media in Spanish in the Basque Country. It is also the denomination used in the Basque version of the Spanish constitution and in the Basque version of the Statute of Autonomy of the Basque Country.

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