Luis Francisco de la Cerda y Aragón, 9th Duke of Medinaceli, by Jacob Ferdinand Voet, circa 1684

Luis Francisco de la Cerda y Aragón, 9th duque de Medinaceli (2 August 1660, El Puerto de Santa María - 26 January 1711, Pamplona), Spanish noble and politician, eldest son of Valido Don Juan Francisco de la Cerda and Doña Catalina de Aragón Folc de Cardona y Córdoba. From his father he inherited the dukedoms of Medinaceli and of Alcalá de los Gazules, along with the marquisates of Cogolludo, of Tarifa, and of Alcalá de la Alameda. From his mother he inherited the dukedoms of Segorbe, of Cardona, of Lerma, and the maquisates of Denia, of Comares, and of Pallars. Moreover twice a Grandee of Spain, he was one of the most important Spanish aristocrats of his time.

During the reign of King Charles II of Spain he served in Italy, being ambassador to the Holy See of Pope Innocent XII, and in 1684 he was made Viceroy and Captain General of Naples; this portrait was likely painted in commemoration of that appointment. He was twenty-four.

From 1699 he was a member of the Spanish Council of State. And when Charles II died his successor, King Philip V, appointed the Duke of Medinaceli Prime Minister of Spain at the beginning of the War of Spanish Succession. More and more opposed to the strong French influence at the Spanish Court, in 1710 he leaked a secret plan to the English about efforts being made to conclude a separate peace between France and the Dutch Republic. For this, he was incarcerated in the Alcázar of Segovia and later transferred to the castle of Pamplona, where he died a prisoner the next year. He was fifty years old.

In 1678, at the age of eighteen, he had married María de las Nieves Girón y Sandoval, daughter of Gaspar Téllez-Girón, 5th Duke de Osuna; she survived him. Their only child had died at the age of three, and at the Duke's death all of his titles were inherited by his nephew, Nicolás Fernández de Córdoba, son of his sister, Feliche María de la Cerda y Aragón. Today, the 19th Duke and head of the house of Medinaceli is Marco de Hohenlohe-Langeburg y Medina, born in 1962, grandson of the 18th Duchess and son of Prince Maximilian von Hohenlohe-Langenburg; a relatively rare mingling of German and Spanish princely blood.