John IV, nicknamed John the Restorer, was the King of Portugal whose reign, lasting from 1640 until his death, began the Portuguese restoration of independence from Habsburg Spanish rule. His accession established the House of Braganza on the Portuguese throne, and marked the end of the 60-year-old Iberian Union by which Portugal and Spain shared the same monarch.

The Restoration War, historically known as the Acclamation War, was the war between Portugal and Spain that began with the Portuguese revolution of 1640 and ended with the Treaty of Lisbon in 1668, bringing a formal end to the Iberian Union. The period from 1640 to 1668 was marked by periodic skirmishes between Portugal and Spain, as well as short episodes of more serious warfare, much of it occasioned by Spanish and Portuguese entanglements with non-Iberian powers. Spain was involved in the Thirty Years' War until 1648 and the Franco-Spanish War until 1659, while Portugal was involved in the Dutch–Portuguese War until 1663.