From the longer Wikipedia page [1]
The Principality of Catalonia (Catalan: Principat de Catalunya, Occitan: Principautat de Catalonha, Latin: Principatus Cathaloniæ), is a historic territory in the northeastern Iberian Peninsula, mostly in Spain and with an adjoining portion in southern France.
It was not until 1258, by the Treaty of Corbeil, that the king of France as heir of Charlemagne and the ancient Frankish Empire did formally relinquish his feudal overlordship over the counties of the Principality of Catalonia to the king of Aragon James I, descendant of Ramon Berenguer IV and heir of the House of Barcelona. This Treaty turned the de facto independence into a full de jure recognition of the Catalan counties as constituent members of the Crown of Aragon, whereas the king of Aragon and count of Barcelona also relinquished any claim over territories in southern France (except the counties of the Roussillon-Vallespir.
The marriage of Isabella I of Castile and Ferdinand II of Aragon (1469) unified two of the three major Christian kingdoms in the Iberian peninsula, while the Kingdom of Navarre was incorporated later following Ferdinand II's 1512 invasion of the Basque kingdom. This resulted in the reinforcement of the concept of Spain, which was already present in the mind of the these kings,[2] made up by the former Crown of Aragon, Castile, and a Navarre annexed to Castile (1515). In 1492, the last remaining portion of Al-Andalus around Granada was conquered and the Spanish conquest of the Americas began.