Kingdom of Sardinia (1720–1861)

The Kingdom of Sardinia was the Savoyard state of the Kingdom of Sardinia from 1720 to 1861. The kingdom united the island of Sardinia with the mainland possessions of the House of Savoy. Before 1847, only the island of Sardinia proper was part of the Kingdom of Sardinia, while the other mainland possessions (principally the Duchy of Savoy, Principality of Piedmont, County of Nice, Duchy of Genoa, and others) were held by the Savoys in their own right, hence forming a composite monarchy and a personal union, which was formally referred to as the "States of His Majesty the King of Sardinia". This situation was changed by the Perfect Fusion act of 1847, which created a unitary kingdom. Due to the fact that Piedmont was the seat of power and prominent part of the entity, the state is also referred to as Sardinia–Piedmont or Piedmont–Sardinia, and sometimes erroneously as the Kingdom of Piedmont.

Before becoming a possession of the House of Savoy, the medieval Kingdom of Sardinia had been part of the Crown of Aragon and then of the burgeoning Spanish Empire. With the Treaty of The Hague (1720), the island of Sardinia and its title of kingdom were ceded by the Habsburg and Bourbon claimants to the Spanish throne to the Duke of Savoy, Victor Amadeus II. The Savoyards united it with their historical possessions on the Italian peninsula, and the kingdom came to be progressively identified with the peninsular states, which included, besides Savoy and Aosta, dynastic possessions like the Principality of Piedmont and the County of Nice, over both of which the Savoyards had been exercising their control since the 13th century and 1388, respectively.

Under Savoyard rule, the kingdom's government, ruling class, cultural models, and centre of population were entirely situated in the peninsula. The island of Sardinia had always been of secondary importance to the monarchy. While the capital of the island of Sardinia and the seat of its viceroys had always been Cagliari by law (de jure), it was the Piedmontese city of Turin, the capital of Savoy since the mid 16th century, which was the de facto seat of power. This situation would be conferred official status with the Perfect Fusion of 1847, when all the kingdom's governmental institutions would be centralized in Turin.

When the peninsular domains of the House of Savoy were occupied and eventually annexed by Napoleonic France, the king of Sardinia temporarily resided on the island for the first time in Sardinia's history under Savoyard rule. The Congress of Vienna (1814–1815), which restructured Europe after Napoleon's defeat, returned to Savoy its peninsular possessions and augmented them with Liguria, taken from the Republic of Genoa. Following Geneva's accession to Switzerland, the Treaty of Turin (1816) transferred Carouge and adjacent areas to the newly-created Swiss Canton of Geneva. In 1847–1848, through an act of Union analogous to the one between Great Britain and Ireland, the various Savoyard states were unified under one legal system with their capital in Turin, and granted a constitution, the Statuto Albertino.

By the time of the Crimean War in 1853, the Savoyards had built the kingdom into a strong power. There followed the annexation of Lombardy (1859), the central Italian states and the Kingdom of the Two Sicilies (1860), Venetia (1866), and the Papal States (1870). On 17 March 1861, to more accurately reflect its new geographic, cultural and political extent, the Kingdom of Sardinia changed its name to the Kingdom of Italy, and its capital was eventually moved first to Florence and then to Rome. The Savoy-led Kingdom of Sardinia was thus the legal predecessor state of the Kingdom of Italy, which in turn is the predecessor of the present-day Italian Republic.