The Duchy of Infantado is a title of Spanish nobility granted by the Catholic Kings on 22 July 1475 to Diego Hurtado de Mendoza and de la Vega, II marquis of Santillana. It gives its name to the House of Infantado.
It is one of the most important noble titles in Spain, and was granted first-class greatness in 1520 by Emperor Charles V.
The Catholic monarchs also created the county of Saldaña in 1479, which would be held by the heirs of the Duchy of Infantado. At that time, the son and heir of Diego Hurtado de Mendoza and de la Vega, was Íñigo López de Mendoza and de la Vega, who became the first count of Saldaña, later the Duke of Infantado.
From that moment all the heirs of the duchy were the counts of Saldaña, also showing the marquisate of Santillana, as the first title that the Mendoza family showed.