Alfonso V of Castile, king of Asturias and León, son of Bermudo II , reigned 999-1027, and was the first who used the title of king of Castile.

He began the work of reorganizing the Christian kingdom of the north-west of the Iberian peninsula after a most disastrous period of civil war and Arab inroads. Enough is known of him to justify the belief that he had some of the qualities of a soldier and a statesman. His name, and that of his wife Geloria (Elvira), are associated with the grant of the first franchises of Leon. He was killed by an arrow while besieging the town of Viseu in northern Portugal, then held by the Muslims.