Juan Alonso Idiáquez, 2nd Duke of Ciudad Real (1597 in Milan – 25 November 1653), was a Spanish noble and naval commander.
He was the son of Alonso de Idiáquez de Butrón y Muxica, an important army commander, who created the Tercio of Idiaquez, and fought many battles in Flanders, Italy and France. For this, he was created Duke of Ciudad Real, Marquis of San Damián, Count of Aramayona and Biandrina. Juan Alonso inherited all these titles from his father.
Juan Alonso became Governor of Cádiz, and it was in this function that he fought two important naval battles.
In 1641, he won the Battle of Cape St. Vincent against a Dutch fleet. Because of this, he was chosen the next year to lead a large Spanish fleet, destined to break the Siege of Perpignan by the French. But he lost the Battle of Barcelona against a French fleet under Jean Armand de Maillé-Brézé.
He became Trece of the Order of Santiago, Governor and Captain General of Galicia and the Basque Country.
He was also Ballestero Mayor, war counsellor and Gentleman of the Bedchamber of King Philip IV of Spain.
He married in 1613 with Ana María de Álava y Guevara, 2nd Countess of Tribiana. They had 3 children: