The Battle of Ourique was a battle that took place on 25 July 1139, in which the forces of Portuguese count Afonso Henriques (of the House of Burgundy) defeated those led by the Almoravid governor of Córdoba, Muhammad Az-Zubayr Ibn Umar, identified as "King Ismar" in Christian chronicles.

Shortly after the battle, Afonso Henriques is said to have called for the first assembly of the estates-general of Portugal at Lamego, where he was given the crown from the Primate Archbishop of Braga, to confirm the Portuguese independence from the Kingdom of León. This was a patriotic falsification perpetuated by the clergy, nobility, and supporters who promoted the restoration of Portuguese sovereignty and the claims of John IV, after the Iberian Union. The documents that refer to the estates-general were "deciphered" by Cistercian monks from the Monastery of Alcobaça to perpetuate the myth and justify the legitimacy of the Portuguese crown in the 17th century.