Philip II (Spanish: Felipe II; 21 May 1527 – 13 September 1598) was King of Spain from 1556 to 1598 and of Portugal from 1581 to 1598 (as Philip I, Filipe I). From 1554 he was King of Naples and Sicily as well as Duke of Milan. During his marriage to Queen Mary I (1554–58), he was also King of England and Ireland. From 1555, he was lord of the Seventeen Provinces of the Netherlands. Known in Spain as "Felipe el Prudente" ('"Philip the Prudent'"), his empire included territories on every continent then known to Europeans, including his namesake the Philippine Islands. During his reign, Spain reached the height of its influence and power. This is sometimes called the Golden Age. The expression, "the empire on which the sun never sets," was coined during Philip's time to reflect the extent of his dominion.

During Philip's reign there were separate state bankruptcies in 1557, 1560, 1569, 1575, and 1596. This was partly the cause for the declaration of independence which created the Dutch Republic in 1581. A devout Catholic, Philip is also known for organising a huge naval expedition against Protestant England in 1588, known usually as the Spanish Armada, which was unsuccessful, mostly due to storms and grave logistical problems.