Ferdinand I of León and Castile

Ferdinand I (c. 1015 – 24 December 1065), called the Great (el Magno), is the Count of Castile from his uncle's death in 1029 and the King of León after defeating his brother-in-law in 1037.

According to tradition, he is the first to have himself crowned Emperor of Spain (1056), and his heirs will carry on the tradition.

He is a younger son of Sancho III of Navarre and Mayor of Castile, and by his father's will recognizes the supremacy of his eldest brother, García Sánchez III of Navarre.

While Ferdinand inaugurates the rule of the Navarrese Jiménez dynasty over western Spain, his rise to preeminence among the Christian rulers of the peninsula shifts the locus of power and culture westward after more than a century of Leonese decline.