Its present form is derived from the Arabic name for Muslim Iberia, “Al-Andalus”. The etymology of the name “Al-Andalus” is disputed, and the extent of Iberian territory encompassed by the name has changed over the centuries.

The Spanish place name Andalucía (immediate source of the English Andalusia) was introduced into the Spanish languages in the 13th century under the form el Andalucía. The name was adopted to refer to those territories still under Moorish rule, and generally south of Castilla Nueva and Valencia, and corresponding with the former Roman province hitherto called Baetica in Latin sources. This was a Castilianization of Al-Andalusiya, the adjectival form of the Arabic language al-Andalus, the name given by the Arabs to all of the Iberian territories under Muslim rule from 711 to 1492. The etymology of al-Andalus is itself somewhat debated (see al-Andalus), but in fact it entered the Arabic language before this area came under Moorish rule.

Like the Arabic term al-Andalus, in historical contexts the Spanish term Andalucía or the English term Andalusia do not necessarily refer to the exact territory designated by these terms today. Initially, the term referred exclusively to territories under Muslim control. Later, it was applied to some of the last Iberian territories to be regained from the Muslims, though not always to exactly the same ones. In the Estoria de España (also known as the Primera Crónica General) of Alfonso X of Castile, written in the second half of the 13th century, the term Andalucía is used with three different meanings:

As a literal translation of the Arabic al-Ándalus when Arabic texts are quoted.

To designate the territories the Christians had regained by that time in the Guadalquivir valley and in the Kingdoms of Granada and Murcia. In a document from 1253, Alfonso X styled himself Rey de Castilla, León y de toda Andalucía (“King of Castile, León and all of Andalusia”).

To designate the territories the Christians had regained by that time in the Guadalquivir valley until that date (the Kingdoms of Jaén, Córdoba and Seville – the Kingdom of Granada was incorporated in 1492). This was the most common significance in the Late Middle Ages and Early modern period.

From an administrative point of view, Granada remained separate for many years even after the completion of the Reconquista due, above all, to its emblematic character as the last territory regained, and as the seat of the important Real Chancillería de Granada, a court of last resort. Still, the reconquest and repopulation of Granada was accomplished largely by people from the three preexisting Christian kingdoms of Andalusia, and Granada came to be considered a fourth kingdom of Andalusia. The often-used expression “Four Kingdoms of Andalusia” dates back in Spanish at least to the mid-18th century.