Nervión is a river that runs through the town of Bilbao, Spain into the Cantabrian Sea. Its lowermost course, downstream of its confluence with the Ibaizabal River, is known as the Estuary of Bilbao.

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.