The Bilbao metro is a rapid transit system serving the city of Bilbao and the region of Greater Bilbao. Lines 1 and 2 have a "Y" shape, as they transit both banks of the river Ibaizabal and then combine to form one line that ends in the south of Bilbao. Line 3 has a "V" shape connecting the municipality of Etxebarri with the Bilbao neighbourhood of Matiko; the apex of the "V" is Zazpikaleak/Casco Viejo station, where all three current lines meet. The metro is connected with the Bilbao tram, Bilboko Aldiriak, Euskotren Trena, Feve, Renfe long-distance trains, and Bilbao's bus station. All three lines use metre gauge.

Bilbao is a city in northern Spain, the largest city in the province of Biscay and in the Basque Country as a whole. It is also the largest city proper in northern Spain. Bilbao is the tenth largest city in Spain, with a population of more than 347,000 as of 2023. The Bilbao metropolitan area has 1,037,847 inhabitants, making it the most populous metropolitan area in northern Spain; with a population of 875,552, the comarca of Greater Bilbao is the fifth-largest urban area in Spain. Bilbao is also the main urban area in what is defined as the Greater Basque region.