The Kingdom of Aragon (Aragonese: Reino d'Aragón, Catalan: Regne d'Aragó, Latin: Regnum Aragonum, Spanish: Reino de Aragón) was a medieval and early modern kingdom on the Iberian Peninsula, corresponding to the modern-day autonomous community of Aragon, in Spain. It should not be confused with the larger Crown of Aragon, that also included other territories - the Principality of Catalonia (which included the County of Barcelona and the other Catalan Counties), the Kingdom of Valencia, the Kingdom of Majorca, and other possessions that are now part of France, Italy, and Greece - that were also under the rule of the King of Aragon, but were administered separately from the Kingdom of Aragon.
Aragon was originally a Carolingian feudal county around the city of Jaca, which in the first half of the 9th century became a vassal state of the kingdom of Pamplona (later Navarre), its own dynasty of counts ending without male heir in 922. The name Aragón is the same as that of the river Aragón, which flows by Jaca.
The Kingdom of Aragón gave the name to the Crown of Aragon, after the dynastic union in 1150 of the Queen of Aragon (Petronilla of Aragon) with a Count of Barcelona (Ramon Berenguer IV), their son inheriting all different territories in the House of Aragon and the House of Barcelona. The Kings of Aragon had also the title of Count of Barcelona and ruled territories that consisted of not only the present administrative region of Aragon but also Catalonia, and later the kingdoms of Majorca, Valencia, Sicily, Naples and Sardinia. The King of Aragón was the direct King of the Aragonese region, and held also the title of Count of Provence, Count of Barcelona, Lord of Montpellier, and Duke of Athens and Neopatria. Each of these titles gave him sovereignty over a certain region, and these titles changed as he lost and won territories. In the 14th century, his power was greatly restricted by the Union of Aragon.
The Crown of Aragon became a part of the Spanish monarchy after the dynastic union with Castile, which supposed the de facto unification of both kingdoms under a common monarch. After this happened, Aragon kept its own institutions, such as the Corts, until the Nueva Planta decrees, promulgated between 1707 and 1715 in the aftermath of the War of the Spanish Succession, finally put an end to it. The decrees ended the kingdoms of Aragon, Valencia and Mallorca and the Principality of Catalonia, and merged them with Castile to officially form the Spanish kingdom. A new Nueva Planta decree in 1711 restored some rights in Aragon, such as the Aragones Civil Right, but preserved the end of the political independence of the kingdom.