Metro Bilbao is a rapid transit (metro) system serving the city of Bilbao and the region of Greater Bilbao. Its lines have a "Y" shape, with two lines that transit both banks of the Nervión river and then combine to form one line that ends in the south of Bilbao. The network of Metro Bilbao is connected with EuskoTran (tram services), Cercanías (commuter rail services), EuskoTren (commuter rail services), FEVE (commuter rail services, regional and long-distance trains) as well as the Renfe service (long-distance trains) and Bilbao's bus station Termibus. It uses a meter gauge.

In total, the Metro has 43.31 km (as of 2011) of rail tracks, with 41 stations (25 of them underground and 16 outside) and 76 accesses (not counting elevators) and 9 substations.

It was the fourth Metro line to be built in Spain, after those in Madrid, Barcelona and Valencia. Currently, it is the third largest Metro company in Spain by number of passengers carried (87,000,000 in 2009) behind the Madrid Metro and the one in Barcelona. It is followed by the metro services of Valencia, Seville and Palma de Mallorca.