Almost half of the 2,155,546 inhabitants of the Basque Autonomous Community live in the Bilbao metropolitan area, almost the entirety of the province of Biscay. Six of the ten most populous cities in the region form part of Bilbao’s conurbation (Bilbao, Barakaldo, Getxo, Portugalete, Santurtzi and Basauri), which is widely known as Greater Bilbao.

With 28.2% of the Basque population born outside this region, immigration is crucial to Basque demographics. Over the 20th century most of this immigration came from other parts of Spain, typically from Galicia or Castile and León. Over recent years, sizeable numbers of this population have returned to their birthplaces and most immigration to the Basque country now comes from abroad, chiefly from South America.

As of 2018, there were 151,519 foreigners in the Basque country, 7% of the population.

Roman Catholicism is, by far, the largest religion in Basque Country. In 2019, the proportion of Basques that identify themselves as Roman Catholic was 60%, while it is one of the most secularised communities of Spain: 24.6% were non-religious and 12.3% of Basques were atheist.