The House of Guzmán (Casa de Guzmán) is an old and noble Spanish family that emerged in Castile in the 12th century and became one of the most prominent dynasties of the Spanish kingdom until the 18th century. The original family gave rise to several branches, one of which became Dukes of Medina Sidonia from the 15th century to the 18th century, in turn giving rise to other branches including the Count-Dukes of Olivares.