The Battle of Aljubarrota is a battle fought between the Kingdom of Portugal and the Crown of Castile on August 14, 1385.

Forces commanded by King John I of Portugal and his general Nuno Álvares Pereira, with the support of English allies, oppose the army of King John I of Castile with its Aragonese, Italian and French allies at São Jorge place, between the towns of Leiria and Alcobaça, in central Portugal.

The result is a decisive victory for the Portuguese, ruling out Castilian ambitions to the Portuguese throne, ending the 1383–85 Crisis and assuring John as King of Portugal.Portuguese independence is confirmed and a new dynasty, the House of Aviz, is established.

Scattered border confrontations with Castilian troops will persist until the death of John I of Castile in 1390, but these will pose no real threat to the new dynasty.

To celebrate his victory and acknowledge divine help, John I of Portugal orders the construction of the monastery of Santa Maria da Vitória na Batalha and the founding of the town of Batalha (Portuguese for "battle").

The king, his wife Philippa of Lancaster, and several of his sons will be buried in this monastery, which is nowadays a UNESCO World Heritage Site.