Gastón de la Cerda, 3rd Duke of Medinaceli

Gastón de la Cerda, 3rd Duke of Medinaceli, Grandee of Spain, (in full, Don Gastón de la Cerda y Portugal, tercer duque de Medinaceli, segundo marqués de Cogolludo, segundo conde del Puerto de Santa María, Grande de España, señor de las villas de Deza, Enciso, Imón y Barahona, antes monje de la Orden de San Jerónimo, después caballero y comendador de la Orden de San Juan de Jerusalén, con honores de Gran Prior en la misma), (c. 1507 – 1552) was a Spanish nobleman.

He was the second son of Don Juan de la Cerda, 2nd Duke of Medinaceli, by first wife Mencía Manuel de Portugal. As a young man he became a monk in the Order of St. Jerome. In 1536 after the death of his elder brother Luis without issue he became the heir to the family titles, so he sought a Papal dispensation in order to marry and fulfill his family obligations. On 4 March 1540 he married María Sarmiento de la Cerda, a marriage that was eventually annulled on 30 August 1544, without issue.