Sancho III (c. 1134 – 31 August 1158), called the Desired (el Deseado),[a] was King of Castile and Toledo for one year, from 1157 to 1158.

His nickname was due to his position as the first child of his parents, born after eight years of childless marriage.

Sancho was the eldest son of King Alfonso VII of León and Castile and Berengaria of Barcelona.

[4] The two brothers had just signed a treaty when Sancho suddenly died in the summer of 1158, being buried at Toledo.

A possible division of the Portuguese kingdom among the two sons of Alfonso VII, would come to nothing due to the premature death of Sancho.