Carlos José Francisco de Paula Gutiérrez de los Ríos y Sarmiento de Sotomayor, 1st Duke of Fernán Núñez (3 January 1779 – 27 November 1822) was a Spanish diplomat.

He was the son of Carlos José Gutiérrez de los Ríos y Rohan-Chabot, 6th Count of Fernán Núñez, and of María de la Esclavitud Sarmiento, 5th Countess of Castel Moncayo. He was born on 3 January 1779 in Lisbon, where his father had served as Ambassador.^[1][2]

He supported Ferdinand, Prince of Asturias in his claim to the throne. After the Tumult of Aranjuez and the abdication of Charles IV in 1808, he was sent to France to help deal with Napoleon. He was sent to negotiate the marriage of Charlotte Bonaparte to the King Ferdinand VII, which was rejected by Napoleon.^[1]

He then became part of a delegation, along with the Dukes of Frías and Medinaceli, that received Napoleon in Bayonne. He joined the entourage of King Joseph I to Spain. After the King left Madrid in July 1808, he joined the War of Independence and was declared a traitor along with several other Dukes by Napoleon. He served as the Ambassador of Spain to London and the Ambassador of Spain to France, where he oversaw the peace treaties following the fall of Napoleon and the succession to the Duchy of Parma.^[1]

He married María Vicenta Solís Vignancourt Lasso de la Vega, 6th Duchess of Montellano, 4th Duchess of Arco, 12th Marquise of Miranda de Anta and 7th Countess of Saldueña (c. 1780 – 4 June 1840) on 29 October 1798. Their marriage was unhappy and they had two children:

• Carlota Gutierrez de los Rios y Solis (25 December 1799 – 1800)^[3]

• María Francisca, 2nd Duchess of Fernán Núñez (4 October 1801 – 26 February 1836). She married Felipe Osorio y de la Cueva, 7th Count of Cervellón (27 June 1795 – 5 February 1859) and they had one daughter.

He died in Paris on 27 November 1822, at the age of 43 due to a horse fall.^[1]