(in Spanish Castilla), an ancient kingdom occupying the central districts of the Spanish peninsula. The history of Castile as a separate kingdom will be found under Spain. The northern part of the kingdom which was first rescued from the dominion of the Moors is called Castilla la Vieja, or Old Castile; the southern, which was a more recent acquisition, is called Castilla la Nueva, or New Castile. They are separated from each other by a lofty chain of sierras which pass under different local names, and stretching in a south-westerly direction from Aragon to Extremadura form the great watershed between the valleys of the Tagus and the Douro. The name of both provinces seems to have been derived from the existence of numerous forts (castillos) erected on the frontiers of the recovered territory to protect them from the reprisals of the enemy.

Old Castile was bounded north by the Bay of Biscay and province of Vizcaya; east by Navarre and Aragon; west by Leon and Asturias; and south by New Castile. It is now divided into the provinces of Burgos, Logroño, Santander, Soria, Segovia, and Avila. These are described under their respective heads. Area, 30,800 square miles. Pop. (1849) 1,037,477.

New Castile was bounded north by Old Castile and Aragon; east by Aragon and Valencia; south by Murcia and Andalusia; and west by Extremadura. It is now divided into the provinces of Madrid, Toledo, Guadalajara, Cuenca and Ciudad Real (La Mancha). These are described under their respective heads. Area 17,720 square miles. Pop. (1849) 1,490,800.