Spain is a multilingual state. Spanish—featured in the 1978 Spanish Constitution as castellano (‘Castilian’)—has effectively been the official language of the entire country since 1931. As allowed in the third article of the Constitution, the other ‘Spanish languages’ can also become official in their respective autonomous communities. The territoriality created by the form of co-officiality codified in the 1978 Constitution creates an asymmetry, in which Spanish speakers’ rights apply to the entire territory whereas vis-à-vis the rest of co-official languages, their speakers’ rights only apply in their territories.

Besides Spanish, other territorialized languages include Aragonese, Aranese, Astur-Leonese, Basque, Ceutan Arabic (Darija), Catalan, Galician, Portuguese and Tamazight, to which the Romani Caló and the sign languages may add up. The number of speakers varies widely and their legal recognition is uneven, with some of the most vulnerable languages lacking any sort of effective protection. Those enjoying recognition as official language in some autonomous communities include Catalan (in Catalonia, the Balearic Islands and the Valencian Community, where it is referred to as ‘Valencian’); Galician (in Galicia); Basque (in the Basque Country and part of Navarre); and Aranese in Catalonia.

Spanish is natively spoken by 74%, Catalan by 17%, Galician by 7% and Basque by 2% of the Spanish population.

Some of the most spoken foreign languages used by the immigrant communities include Moroccan Arabic, Romanian and English.