At the end of the 11th century, the Burgundian knight Henry became count of Portugal and defended its independence by merging the County of Portugal and the County of Coimbra. His efforts were assisted by a civil war that raged between León and Castile and distracted his enemies. Henry's son Afonso Henriques took control of the county upon his death. The city of Braga, the unofficial Catholic centre of the Iberian Peninsula, faced new competition from other regions. Lords of the cities of Coimbra and Porto fought with Braga's clergy and demanded the independence of the reconstituted county.

The Battle of São Mamede took place on 24 June 1128 near Guimarães and is considered the seminal event for the foundation of the Kingdom of Portugal and the battle that ensured Portugal's Independence. Portuguese forces led by Afonso Henriques defeated forces led by his mother Teresa of Portugal and her lover Fernão Peres de Trava. Following São Mamede, the future king styled himself "Prince of Portugal". He would be called "King of Portugal" starting in 1139 and was recognised as such by neighbouring kingdoms in 1143.