The County of Barcelona is originally a frontier region under the rule of the Carolingian dynasty.

By the end of the 10th century, the Counts of Barcelona are de facto independent, hereditary rulers in constant warfare with the Islamic caliphate of Córdoba and its successor states.

The counts, through marriage alliances and treaties, acquire the other Catalan counties and extend their influence along Occitania.

Barcelona forms the nucleus of the emergent Principality of Catalonia.

In 1164, the count of Barcelona, Alfons I, inherites the Kingdom of Aragon (as Alfonso II).

Henceforward, the history of the county of Barcelona is subsumed within that of the Crown of Aragon, but the city of Barcelona remains preeminent within it.