Juan Alonso Idiáquez, 2nd Duke of Ciudad Real (1597 in Milan – 25 November 1653), was a Spanish noble and naval commander.
For this, he was created Duke of Ciudad Real, Marquis of San Damián, Count of Aramayona and Biandrina.
Juan Alonso then became Governor of Cádiz, and it was in this function that he fought two important naval battles.
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.
He was also Ballestero Mayor, war counsellor and Gentleman of the Bedchamber of King Philip IV of Spain.