Spain has a total of 70 functional urban areas (AUF), or metropolitan areas, as defined by the European Union. Each AUF is formed by a city and all those municipalities that form its functional environment.
To determine if a municipality belongs to a functional urban area, the criterion used is that of employment: if 15% or more of its employed population moves to the reference city for work reasons, then it belongs to that AUF.
In 2017, the Spanish functional urban areas with the largest population were those of Madrid (6.71 million inhabitants), Barcelona (4.96 million) and Valencia (1.72 million), according to the latest data in the report Indicators Urban published by the National Institute of Statistics (INE).
The fourth position corresponded to Seville (1.54 million), while Bilbao (1.03 million) was the fifth.
The rest of the Spanish metropolitan areas already have less than one million inhabitants. After the first five were Malaga (858,731 inhabitants), Zaragoza (756,296), Palma de Mallorca (678,611), Las Palmas de Gran Canaria (630,413) and Murcia (624,658).
The following graph shows the ranking of the 70 Spanish functional urban areas according to their population in 2017: