king of Castile from 1065 to 1072, the eldest son of Ferdinand I.

He was allocated the kingdom of Castile in his father's will, Leon and Galicia being given to his brothers. He refused to accept this division and dispossessed García of Galicia by force (1071). Alfonso VI of Leon, defeated at Golpejera on the Carrión River in January 1072, had to seek refuge with the Moorish king of Toledo. Sancho's triumph was short-lived, for he was killed while besieging the rebel fortress-city of Zamora, held by his sister Urraca in Alfonso's name.

fourth king of Portugal, son of Afonso II and of Urraca, who was the daughter of Alfonso VIII of Castile.

Factions were so fostered during Sancho's minority that his later government was never anything more than a series of vain attempts to achieve political stability in the kingdom. Renewing the struggle against the Moors, he took Tavira and Cacela (1238–39), thereby extending Portuguese sovereignty over a large part of the Algarve. But from 1240 onward internal disorders increased, and Pope Innocent IV's recognition of the king's political incapacity to govern led to Sancho's deposition (1245) and the entrusting of the administration to his brother Afonso (later Afonso III). Sancho retired to Toledo (1247), where he died the next year.