Alfonso II, called the Chaste or the Troubadour, was the King of Aragon and, as Alfons I, the Count of Barcelona from 1164 until his death. The eldest son of Count Ramon Berenguer IV of Barcelona and Queen Petronilla of Aragon, he was the first King of Aragon who was also Count of Barcelona. He was also Count of Provence, which he secured from Douce II and her would-be father-in-law Raymond V, Count of Toulouse, from 1166 until 1173, when he ceded it to his brother, Ramon Berenguer III. His reign has been characterised by nationalistic and nostalgic Catalan historians as l'engrandiment occitànic or "the Pyrenean unity": a great scheme to unite various lands on both sides of the Pyrenees under the rule of the House of Barcelona.

The count of Barcelona was the ruler of the County of Barcelona and also, by extension and according with the Usages and Catalan constitutions, of the Principality of Catalonia as Princeps for much of Catalan history, from the 9th century until the 18th century. After 1164, with Alfonso II of Aragon and I of Barcelona, the title of count of Barcelona was united with that of king of Aragon, and after the 16th century, with that of king of Spain.