The Spanish Armada (a.k.a. the Invincible Armada or the Enterprise of England, Spanish: Grande y Felicísima Armada, lit. 'Great and Most Fortunate Navy') was a Spanish fleet that sailed from Lisbon in late May 1588, commanded by the Duke of Medina Sidonia, an aristocrat without previous naval experience appointed by Philip II of Spain. His orders were to sail up the English Channel, link up with the Duke of Parma in Flanders, and escort an invasion force that would land in England and overthrow Elizabeth I. Its purpose was to reinstate Catholicism in England, end support for the Dutch Republic, and prevent attacks by English and Dutch privateers against Spanish interests in the Americas.

The Spanish were opposed by an English fleet based in Plymouth. Faster and more manoeuvrable than the larger Spanish galleons, they were able to attack the Armada as it sailed up the Channel. Several subordinates advised Medina Sidonia to anchor in The Solent and occupy the Isle of Wight, but he refused to deviate from his instructions to link up with Parma. Although the Armada reached Calais largely intact, while awaiting communication from Parma, it was attacked at night by English fire ships and forced to scatter.

The Armada suffered further losses in the ensuing Battle of Gravelines, and was in danger of running aground on the Dutch coast when the wind changed, allowing it to escape into the North Sea. Pursued by the English, the Spanish ships returned home via Scotland and Ireland. Up to 24 ships were wrecked along the way before the rest managed to get home.

The expedition was the largest engagement of the undeclared Anglo-Spanish War. The following year, England organized a similar large-scale campaign against Spain, the English Armada, sometimes called the "counter-Armada of 1589", which was also a failure.