The House of Castro is an Iberian noble lineage, beginning mainly in the kingdoms of Castile, Galicia, and Portugal.

The first clearly identified member of the family was early-12th century count Fernando García de Hita, a kinsman and vassal of Urraca of León and Castile.

This kinship, along with his patronymic, have led to his being considered an illegitimate son of Urraca's uncle García II of Galicia.

[1] More recently, it has been suggested that he was the son of count García Ordóñez by the infanta Urraca Garcés of Navarre, and perhaps scion of the Banu Gómez clan.

The lack of heirs in the senior line resulted in the rise of a cadet branch seated in Galicia.