Dom Afonso VI (Portuguese pronunciation: [ɐˈfõsu]; 21 August 1643 – 12 September 1683), known as "the Victorious" (o Vitorioso), was the second king of Portugal of the House of Braganza from 1656 until his death.

[4] In 1668, his brother Pedro II conspired to have him declared incapable of ruling, and took supreme de facto power as regent, although nominally Afonso was still sovereign.

[13] After the death of his eldest brother Teodósio, Prince of Brazil in 1653, Afonso became the heir apparent to the throne of the kingdom.

[11][10] In 1662, after Afonso terrorized Lisbon at night alongside his favorites,[17][18] Luisa and her council responded by banishing some of the king's companions that were associated with the raids.

[20] His astute military organization and sensible general appointments resulted in decisive military victories over the Spanish[25] at Elvas (14 January 1659), Ameixial (8 June 1663) and Montes Claros (17 June 1665),[26][27] culminating in the final Spanish recognition of sovereignty of Portugal's new ruling dynasty, the House of Braganza,[28][29] on 13 February 1668 in the Treaty of Lisbon.

[29][43] His health broken by this captivity, he was eventually permitted to return to the Portuguese mainland, but he remained powerless and kept under guard.