Spain
As a percentage of the general population of all Spain, Spanish is natively spoken by 74%, Catalan by 17%, Galician by 7% and Basque by 2% of all Spaniards. Occitan is spoken by less than 5,000 people, only in the small region of "Val d'Aran".
Other Romance minority languages, though not official, have special recognition, such as the Astur-Leonese language ("asturianu", "bable" or "llionés") and Aragonese ("aragonés") in Aragon.
Castilians
Castilian ("castellano"), that is, Spanish, is the native language of the Castilians. Its origin is traditionally ascribed to an area south of the Cordillera Cantábrica, including the upper Ebro valley, in northern Spain, around the 8th and 9th centuries; however the first written standard was developed in the 13th century in the southern city of Toledo. It is descended from the Vulgar Latin of the Roman Empire, with Arabic influences, and perhaps Basque as well. During the Reconquista in the Middle Ages, it was brought to the south of Spain where it replaced the languages that were spoken in the former Moorish controlled zones, such as the local form of related Latin dialects now referred to as Mozarabic, and the Arabic that had been introduced by the Muslims. In this process Castilian absorbed many traits from these languages, some of which continue to be used today. Outside of Spain and a few Latin American countries, Castilian is now usually referred to as "Spanish".