Ferdinand III (; 1199/120130 May 1252), called the Saint ("el Santo"), was King of Castile from 1217 and King of León from 1230 as well as King of Galicia from 1231. He was the son of Alfonso IX of León and Berenguela of Castile. Through his second marriage he was also Count of Aumale. Ferdinand III was one of the most successful kings of Castile, securing not only the permanent union of the crowns of Castile and León, but also masterminding the most expansive campaign of Reconquista yet.