Ferdinand of León (died 1214)

Ferdinand (c. 1192 – August 1214) was the eldest son and heir apparent of Alfonso IX of León by his first wife, Theresa, daughter of Sancho I of Portugal.

With her former husband's assistance she hoped to secure the wealth of properties that had been left to her in her father's will against the claims of the Portuguese crown.

From 21 April 1211, Ferdinand, whose legitimacy was suspect on account of his parents' annulment, was the heir apparent to the throne of León.

Although the treaty weakened the Castilian defences on the border by forcing them to hand over four castles to the Leonese to be demolished, it probably also strengthened the position of Alfonso VIII's grandson against the eldest son Ferdinand in a possible future succession crisis.

Ferdinand was a co-signatory with his father in several acts before April that year, when the two kingdoms made peace in preparation for a great battle against the Muslims.