The Judicate of Arborea or the Kingdom of Arborea was one of the four independent judicates into which the island of Sardinia was divided in the Middle Ages. It occupied the central-west portion of the island, wedged between Logudoro to the north and east, Cagliari to the south and east, and the Mediterranean Sea to the west. To the northeast and beyond Logudoro was Gallura, with which Arborea had far less interaction. Arborea outlasted her neighbours, surviving well into the 15th century. At its greatest territorial extent it occupied the entire island except the cities of Alghero and Cagliari. The earliest known judicial seat was Tharros, though Oristano served as capital for most of its existence.

Cagliari is an Italian municipality and the capital and largest city of the island of Sardinia, an autonomous region of Italy. It has about 155,000 inhabitants, while its metropolitan city has about 420,000 inhabitants. According to Eurostat, the population of the functional urban area, the commuting zone of Cagliari, rises to 476,975. Cagliari is the 26th largest city in Italy and the largest city on the island of Sardinia.