Alfonso X was a Castilian

Crown of Castile

The Crown of Castile was a medieval and modern state in the Iberian Peninsula that formed in 1230 as a result of the third and definitive union of the crowns and parliaments of the kingdoms of Castile and León upon the accession of the then King Ferdinand III of Castile to the vacant Leonese throne...

 monarch who ruled as the King of Castile

Crown of Castile

The Crown of Castile was a medieval and modern state in the Iberian Peninsula that formed in 1230 as a result of the third and definitive union of the crowns and parliaments of the kingdoms of Castile and León upon the accession of the then King Ferdinand III of Castile to the vacant Leonese throne...

, León

Kingdom of León

The Kingdom of León was an independent kingdom situated in the northwest region of the Iberian Peninsula. It was founded in AD 910 when the Christian princes of Asturias along the northern coast of the peninsula shifted their capital from Oviedo to the city of León...

 and Galicia

Kingdom of Galicia

The Kingdom of Galicia was a political entity located in southwestern Europe, which at its territorial zenith occupied the entire northwest of the Iberian Peninsula. Founded by Suebic king Hermeric in the year 409, the Galician capital was established in Braga, being the first kingdom which...

 from 1252 until his death. He also was elected King of the Germans in 1257.

He established Castilian

Castilian Spanish

Castilian Spanish is a term related to the Spanish language, but its exact meaning can vary even in that language. In English Castilian Spanish usually refers to the variety of European Spanish spoken in north and central Spain or as the language standard for radio and TV speakers...

 as a language of higher learning and earned his nicknames "the Wise" or "the Learned" and "the Astrologer" through his own prolific writings, including Galician poetry

Galician-Portuguese lyric

In the Middle Ages, the Galician-Portuguese lyric, sometimes called trovadorismo in Portugal and trobadorismo in Galicia, was a lyric poetic school or movement. All told, there are around 1680 texts in the so-called "secular lyric" or lírica profana...

.
Born in Toledo, Spain, Alfonso was the eldest son of Ferdinand III of Castile

Ferdinand III of Castile

Saint Ferdinand III, T.O.S.F., was the King of Castile from 1217 and León from 1230. He was the son of Alfonso IX of León and Berenguela of Castile. Through his second marriage he was also Count of Aumale. He finished the work done by his maternal grandfather Alfonso VIII and consolidated the...

 and Elisabeth of Hohenstaufen

Elisabeth of Hohenstaufen

Beatrice of Swabia was Queen of Castile and Leon as the wife of King Ferdinand III...

, known in Spain as Beatriz de Suabia, through whom he was a cousin of Frederick II, Holy Roman Emperor

Frederick II, Holy Roman Emperor

Frederick II , was one of the most powerful Holy Roman Emperors of the Middle Ages and head of the House of Hohenstaufen. His political and cultural ambitions, based in Sicily and stretching through Italy to Germany, and even to Jerusalem, were enormous...

, to whom Alfonso is often compared.