The Crown of Aragon (US: ) was a composite monarchy ruled by one king, originated by the dynastic union of the Kingdom of Aragon and the County of Barcelona (later Principality of Catalonia) and ended as a consequence of the War of the Spanish Succession. At the height of its power in the 14th and 15th centuries, the Crown of Aragon was a thalassocracy controlling a large portion of present-day eastern Iberian Peninsula, parts of what is now southern France, and a Mediterranean empire which included the Balearic Islands, Sicily, Corsica, Sardinia, Malta, Southern Italy (from 1442), and parts of Greece (until 1388).
The component realms of the Crown were not united politically except at the level of the king, who ruled over each autonomous state according to its own laws, raising funds under each tax structure, and dealing separately with each Corts or Cortes (parliaments), particularly in the Kingdom of Aragon, the Principality of Catalonia, and the Kingdom of Valencia. The larger Crown of Aragon must not be confused with one of its constituent parts, the Kingdom of Aragon, from which it takes its name.
In 1479, a new dynastic union of the Crown of Aragon with the Crown of Castile by the Catholic Monarchs, joining what contemporaries referred to as "the Spains", led to what would become the Spanish composite monarchy under Habsburg monarchs. The Aragonese Crown continued to exist until it was abolished by the Nueva Planta decrees issued by King Philip V in 1707–1716 as a consequence of the defeat of Archduke Charles (as Charles III of Aragon) in the War of the Spanish Succession.
Formally, the political centre of the Crown of Aragon was Zaragoza, where kings were crowned at La Seo Cathedral. The 'de facto' capital and leading cultural, administrative and economic centre of the Crown of Aragon was Barcelona, followed by Valencia. Palma (Mallorca) also functioned as an additional important city and seaport.
The Crown of Aragon eventually included the Kingdom of Aragon, the Principality of Catalonia (until the late 12th century the County of Barcelona and others), the Kingdom of Valencia, the Kingdom of Majorca, the Kingdom of Sicily, Malta, the Kingdom of Naples and Kingdom of Sardinia. For brief periods the Crown of Aragon also controlled Montpellier, Provence, Corsica, and the twin Duchy of Athens and Neopatras in Latin Greece.
In the Late Middle Ages, the southward territorial expansion of the Aragonese Crown in the Iberian Peninsula stopped in Murcia, which eventually consolidated as a realm of the Crown of Castile, the Kingdom of Murcia. Subsequently, the Aragonese Crown focused on the Mediterranean, governing as far afield as Greece and the Barbary Coast. In contrast, Portugal, which completed its southward expansion in 1249, would focus on the Atlantic Ocean. Mercenaries from the territories in the Crown, known as Almogavars participated in the creation of this Mediterranean empire, and later found employment in countries all across southern Europe.
The Crown of Aragon has been considered an empire which ruled in the Mediterranean for centuries, with thalassocratic power to setting rules over the entire sea, (as documented, for instance, in the Llibre del Consolat del Mar or Book of the Consulate of the Sea, written in Catalan, is one of the oldest compilations of maritime laws in the world).
However, the different territories were only connected through the monarch's person. A modern historian, Juan de Contreras y Lopez de Ayala, marquis of Lozoya, described the Crown of Aragon as being more like a confederacy than a centralised kingdom.
The Crown of Aragon originated in 1137, when the Kingdom of Aragon and the County of Barcelona (along with the County of Provence, Girona, Cerdanya, Osona, and other territories) merged by dynastic union upon the marriage of Petronilla of Aragon and Raymond Berenguer IV of Barcelona; their individual titles combined in the person of their son Alfonso II of Aragon, who ascended to the throne in 1162. This union respected the existing institutions and parliaments of both territories. The combined state was initially known as Regno, Dominio et Corona Aragonum et Catalonie (only between 1286 and 1291), and later as Corona Regum Aragoniae, Corona Aragonum or simply Aragon.
Petronilla's father King Ramiro, "The Monk" (reigned 1134–1137) who was raised in the Monastery of Saint Pons de Thomières, Viscounty of Béziers as a Benedictine monk was the youngest of three brothers. His brothers Peter I (reigned 1094–1104) and Alfonso I El Batallador (The Battler, reigned 1104–1134) had fought against Castile for hegemony in the Iberian peninsula. Upon the death of Alfonso I, the Aragonese nobility that campaigned close to him feared being overwhelmed by the influence of Castile. And so, Ramiro was forced to leave his monastic life and proclaim himself King of Aragon. He married Agnes, sister of the Duke of Aquitaine and betrothed his only daughter Petronilla of Aragon to Raymond Berenguer IV, Count of Barcelona. The wedding agreement provided Berenguer with the title of Princeps Aragonum and Dominator Aragonensis (Ruler of the Kingdom and Commander of the Aragonese Military) but the title of King of Aragon was reserved for Ramiro II and Berenguer's future sons.
Raymond Berenguer IV, the first ruler of the united dynasty, called himself Count of Barcelona and "Prince of Aragon".
Alfonso II inherited two realms and with them, two different expansion processes. The House of Jiménez looked south in a battle against Castile for the control of the middle valley of the Ebro in the Iberian peninsula. The House of Barcelona looked north to its origins, Occitania, where through family ties it had significant influence, especially in Toulouse, Provence and Foix, towards the south along the Mediterranean coast and towards the Mediterranean sea.
Soon, Alfonso II of Aragon and I of Barcelona committed to conquering Valencia as the Aragonese nobility demanded. Like his father, he gave priority to the expansion and consolidation of the House of Barcelona's influence in Occitania.
Alfonso II signed the treaties of Cazorla, a multilateral treaty between Navarre, Aragon, León, Portugal, and Castile to redefine the frontiers and zones of expansion of each kingdom. Alfonso II assured Valencia by renouncing the Aragonese rights of annexing Murcia in exchange for securing the Aragonese frontier with Castile. This action should be seen as result of the aforementioned priority given over the Occitan and Catalan dominions of the Crown of Aragon.
From the ninth century, the dukes of Aquitaine, the kings of Navarre, the counts of Foix, the counts of Toulouse and the counts of Barcelona were rivals in their attempts at controlling the various counties of the Hispanic Marches and pays of Occitania. And the House of Barcelona succeeded in extending its influence to the area that is now south of France through strong family ties, in the areas of the County of Provence, County of Toulouse and County of Foix. The rebellion of the Cathars or Albigensians, who rejected the authority and teachings of the Catholic Church, led to the loss of these possessions in southern France. Pope Innocent III called upon Philip II of France to suppress the Albigensians—the Albigensian Crusade, which led to bringing Occitania firmly under the control of the King of France, and the Capetian dynasty from northern France.
Peter II of Aragon returned from the Battle of Las Navas de Tolosa in autumn 1212 to find that Simon de Montfort, 5th Earl of Leicester, had conquered Toulouse, exiling Count Raymond VI of Toulouse, who was Peter's brother-in-law and vassal. Peter's army crossed the Pyrenees and arrived at Muret where they were joined by Raymond of Foix and Raymond of Toulouse's forces, in September 1213 to confront Montfort's army. The Battle of Muret began on 12 September 1213. The Catalan, Aragonese and Occitan forces were disorganised and disintegrated under the assault of Montfort's squadrons. Peter himself was caught in the thick of fighting, and died as a result of a foolhardy act of bravado. Thus, the nobility of Toulouse, Foix and other vassals of the Crown of Aragon were defeated. The conflict concluded with the Treaty of Meaux-Paris in 1229, in which the Crown of Aragon agreed to renounce its rights over the south of Occitania with the integration of these territories into the dominions of the King of France.