Castille

Castile is a historical region of Spain, located in the center of the Iberian Peninsula. It was once the most powerful of the medieval Christian kingdoms of Iberia, eventually giving its name to the modern Kingdom of Spain. The name "Castile" derives from the numerous castles (castillos) built in the region during the Reconquista. Its territory was largely formed between the 9th and 11th centuries as a frontier march of the Kingdom of Asturias.

The Kingdom of Castile grew and expanded southwards through centuries of conflict with the Moors. A pivotal moment in its history was the union with the Crown of Aragon in 1469 through the marriage of Ferdinand II of Aragon and Isabella I of Castile. This union laid the groundwork for the formation of modern Spain. Castile played a dominant role in the subsequent unification and expansion of the Spanish Empire.

Historically, Castile was divided into Old Castile and New Castile, though these were administrative rather than strictly geographical divisions. Today, the historical territory of Castile is mainly encompassed by the autonomous communities of Castile and León and Castile-La Mancha, along with parts of Madrid and Cantabria. The Castilian language, or Spanish, originated in this region and became the dominant language of Spain and much of the Americas.