Alonso de Guzmán y Sotomayor, 7th Duke of Medina Sidonia

Portrayed wearing the Order of the Golden Fleece, c. 1612
Born10 September 1550
Died26 July 1615(1615-07-26) (aged 64)
Sanlúcar de Barrameda, Cádiz, Castile, Spain
Allegiance Spain
Branch Spanish Navy
RankCaptain-General of the Ocean Sea
Captain-General of the Coast of Andalusia
CommandsInvasion of England
('the Spanish Armada')
ConflictsWar of the Portuguese Succession
Anglo–Spanish War (1585–1604)

Alonso Pérez de Guzmán y de Zúñiga-Sotomayor, 7th Duke of Medina Sidonia, GE (10 September 1550 – 26 July 1615), was a Spanish aristocrat who was most noted for his role as commander of the Spanish Armada that was to attack Southern England in 1588. He was a great-great grandson of Ferdinand II of Aragon.

He was one of the wealthiest men in Europe and a patron of the arts. Successful for his prodigious logistic ability, he organized naval defense and commerce in the southern Iberian Peninsula, managing fleets and pioneering the usage of vessels like frigates. Despite this, he was not personally a naval commander, which contributed to the failure of the Spanish Armada, entrusted to him against his judgement. His defective performance during the battle marked his career in late historiography.