The Battle of Trancoso was fought on 29 May 1385^[2] between the Kingdom of Portugal and the Crown of Castile.

Following the coronation of João of Aviz, John I of Castile sent an army into the Portuguese region of Beira in retaliation for Portuguese defiance, where they committed all the kinds of atrocities.^[3] The city of Viseu was pillaged and burned,^[4] but when the Castilians were returning to Castile with their plundered loot and the prisoners they had taken, a Portuguese army met them, dismounted and assumed a defensive formation. The Castilians exhausted themselves in attack but ended up being utterly routed,^[5][6] with very high casualties among their ranks, and with six of their seven captains killed.^[7] The Portuguese released all those taken captive by the Castilians and recovered all the pillage taken from their towns.^[8]