1383–1385 Portuguese interregnum

1383–1385 Portuguese interregnum
	Part of the Hundred Years' War
	; The Battle of Aljubarrota by Jean de Wavrin
Date	2 April 1383 – 15 October 1385
Location	Portugal and Castile
Result	Victory of the Grandmaster of Avis's party: John of Avis becomes John I of Portugal, ushering in the Johanine Dynasty; Consolidation of Portuguese independence from Castile.; Signing of the Treaty of Windsor, strengthening the Anglo-Portuguese Alliance and kickstarting the so-called "Illustrious Generation";
Belligerents
Party of the Grandmaster of Avis; Supported by:; England	Party of Beatrice of Portugal; Castile; Supported by:; France; Aragon; Genoese volunteers
Commanders and leaders
John, Grandmaster of Avis; Nuno Álvares Pereira	Beatrice, Queen-consort of Castile; John I of Castile; Fernando Sánchez de Tovar #; Pedro Álvares Pereira †

The 1383–1385 Portuguese interregnum (Portuguese: Interregno (português) de 1383–1385) was a war of succession in Portuguese history during which no crowned king of Portugal reigned. The interregnum began when King Ferdinand I died without a male heir and ended when King John I was crowned in 1385 after his victory during the Battle of Aljubarrota.

The Portuguese interpret the era as their earliest national resistance movement to counter Castilian intervention, and Robert Durand considers it as the "great revealer of national consciousness".

The bourgeoisie and the nobility worked together to establish the Avis dynasty, a branch of the Portuguese House of Burgundy, securely on an independent throne. That contrasted with the lengthy civil wars in France (Hundred Years' War) and England (War of the Roses), which had aristocratic factions fighting powerfully against a centralised monarchy.

In Portugal it is sometimes known simply as the Interregnum (or the First Interregnum, if the 1580 Portuguese succession crisis is counted as a "Second Interregnum"), the 1383–1385 crisis (Crise de 1383–1385) or the Avis Revolution (Revolução de Avis).