Portuguese Interregnum

The Portuguese succession crisis and civil conflict of 1383–1385, resolved when John I became king and founded the House of Aviz.

Ferdinand I of Portugal: King of Portugal from 1367 to 1383, whose death without a male heir triggered a succession crisis. His death left the crown contested between his daughter Beatrice and rival claimants.
House of Burgundy (Portugal): The Portuguese royal dynasty descended from Henry of Burgundy, which ruled Portugal until 1383. Its extinction in the male line left Ferdinand I’s daughter as the principal dynastic heir.
House of Aviz: The Portuguese royal dynasty founded by John I, which ruled from 1385 to 1580. Its establishment was the lasting dynastic result of the crisis.
Portuguese succession crisis of 1580: The succession dispute that ended with Philip II of Spain becoming king of Portugal in 1580. Unlike the 1383–1385 outcome, this crisis placed Portugal under a Spanish monarch.
Beatrice of Portugal: The only surviving child of Ferdinand I of Portugal and queen consort of Castile through her marriage to John I of Castile. Her claim to Portugal, backed by her Castilian husband, became the crisis’s central dynastic rival.
Treaty of Salvaterra de Magos: A 1383 agreement arranging the marriage of Beatrice of Portugal to John I of Castile and addressing the Portuguese succession. Its terms sought to protect Portuguese independence but made the Castilian king central to the succession.
Anglo-Portuguese Alliance: The long-standing alliance between England and Portugal, formalized by the Treaty of Windsor in 1386. English support during the crisis helped create the conditions for its formal alliance.
Miguel of Portugal: A claimant to the Portuguese throne during the succession crisis of 1383–1385, supported by some nobles. His rival claim shows that the conflict involved more than the contest between Beatrice and John.
John I of Portugal: King of Portugal from 1385 to 1433 and founder of the House of Aviz. The Cortes acclaimed him king after his forces defeated the Castilian invasion.
John I of Castile: King of Castile from 1379 to 1390 and husband of Beatrice of Portugal. His claim through Beatrice and invasion of Portugal turned a succession dispute into war.

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