The Kingdom of Sardinia comprised initially the island of Sardinia, first as a part of the Crown of Aragon and subsequently the Spanish Empire (1297–1720), and second as a part of the composite state of the House of Savoy (1720–1861), giving his name to the entire State. Its capital was originally Cagliari, in the south of the island, and later Turin, on the mainland. The kingdom was formed by Pope Boniface VIII from a papal claim to the islands of Corsica and Sardinia in 1297 and bestowed, as a vassal of the Holy See, on James II of Aragon. It was not until 1324 that James launched a military campaign to take control of his kingdom, and not until 1448 that the last resistance fell. In 1416 the first of a long line of viceroys was appointed, and in 1420 the main competing claim to the island was bought out.

From 1516 the Aragonese and by extension the Sardinian crown were in personal union with the Kingdom of Castile and thus formed a part of the much larger Spanish Empire. During this period the Spanish language was introduced for administration. In 1713, following the War of the Spanish Succession, the Kingdom of Sardinia was ceded to the Habsburgs by the Treaty of Utrecht for the loss of their Spanish kingdoms. By the same treaty Victor Amadeus II, Duke of Savoy, received the Kingdom of Sicily, supplying him with the coveted royal rank. By 1720 the balance of power had shifted again and the House of Savoy was forced to exchange Sicily with the Habsburgs for Sardinia (Treaty of The Hague). At that time the Kingdom of Sardinia refers to the states of the House of Savoy from 1720 or 1723 onwards (also known as Piedmont-Sardinia), following the award of the crown of Sardinia to King Victor Amadeus II of Savoy under the Treaty of The Hague (1720).