Fernando Álvarez de Toledo, 3rd Duke of Alba

Fernando Álvarez de Toledo y Pimentel, 3rd Duke of Alba (29 October 1507 – 11 December 1582), known as the Grand Duke of Alba (Spanish: Gran Duque de Alba, Portuguese: Grão Duque de Alba) in Spain and Portugal and as the Iron Duke (Dutch: IJzeren Hertog) or shortly 'Alva' in the Netherlands and Belgium, was a Spanish military officer, statesman and diplomat.

He has often been considered the most effective general of his generation, as well as one of the greatest in history. Historian John Lothrop Motley wrote of him "no man had studied military science more deeply, or practiced it more constantly" at his day. He was a royal promoter of military action against France and Protestantism, although he also defended a moral and strategic alliance with England that never realized. Alba achieved notoriety for his role during the Eighty Years' War in the Spanish Netherlands, where his prolonged campaigns and repressive political actions caused his figure to be reviled in European history as a symbol of tyranny.

Born into a prominent Castilian military family, Alba first distinguished himself in the 1535 conquest of Tunis during the Ottoman–Habsburg Wars as part of a long conflict for predominance over the western Mediterranean Sea. He then commanded the Spanish troops at the Battle of Mühlberg (1547), where the army of Holy Roman Emperor Charles V defeated the German Protestant princes in the Schmalkaldic War. Alba was the commander-in-chief of the Spanish-Habsburg army during the Italian War of 1551–1559, and became governor of Milan in 1555 and viceroy of Naples in 1556.

In 1567, King Philip II of Spain appointed Alba governor of the Netherlands and tasked him with the suppression of Dutch rebels. Alba instituted the Council of Troubles, which led to the condemnations of thousands and came to be known as the "Council of Blood". Alba repeatedly defeated the troops of William of Orange during the first stages of the Eighty Years' War, but failed to extinguish politically the rebellion, and in 1573 he was recalled to Spain in temporary political disgrace. Alba's last military successes were in the Portuguese succession crisis of 1580, for which he was rewarded the titles viceroy and constable of Portugal. He held both titles until his death in Lisbon in 1582.