Duke of Savoy in the context of "Savoy"

The term Kingdom of Sardinia denotes the Savoyard state from 1720 to 1861. From 1720 to 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 House of Savoy 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. Regardless, historians often use "Sardinia" as a synecdoche to designate the whole Savoyard state from 1720. 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.

Victor Amadeus II (Italian: Vittorio Amedeo Francesco, Arpitan: Victor-Amèdê, French: Victor-Amédée; 14 May 1666 – 31 October 1732) was the head of the House of Savoy and ruler of the Savoyard states from 12 June 1675 until his abdication in 1730. He was the first of his house to acquire a royal crown, ruling first as King of Sicily (1713–1720) and then as King of Sardinia (1720–1730). Among his other titles were Duke of Savoy, Duke of Montferrat, Prince of Piedmont, Marquis of Saluzzo and Duke of Aosta, Maurienne and Nice.

Louis XIV arranged his marriage in order to maintain French influence in Savoy, but Victor Amadeus soon broke away from the influence of France. At his father's death in 1675, his mother, Marie Jeanne Baptiste of Nemours, was regent in the name of her nine-year-old son and would remain in de facto power until 1684 when Victor Amadeus banished her further involvement in the state. Having fought in the War of the Spanish Succession, he was rewarded with the Kingdom of Sicily in 1713, but he was forced to exchange this title for the poorer Kingdom of Sardinia in 1720.

Amadeus VIII (4 September 1383 – 7 January 1451), nicknamed the Peaceful, was Count of Savoy from 1391 to 1416 and Duke of Savoy from 1416 to 1440. He was the first to hold the ducal title, granted by Emperor Sigismund. Known for his diplomatic temperament and administrative reforms, he strengthened the state's institutions and fostered internal peace.

He also claimed the papacy from 1439 to 1449 as Antipope Felix V, in opposition to Popes Eugene IV and Nicholas V, becoming the last historical antipope recognised by a significant portion of the Catholic clergy.
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Charles Emmanuel III (27 April 1701 – 20 February 1773) was Duke of Savoy, King of Sardinia and ruler of the Savoyard states from his father's abdication on 3 September 1730 until his death in 1773. He was the paternal grandfather of the last three mainline kings of Sardinia. In the War of the Polish Succession, he initially gained Lombardy but later ceded it for smaller territorial gains. During the War of the Austrian Succession, he defended Piedmont against a Franco-Spanish army, winning the Battle of Assietta. The Treaty of Aix-la-Chapelle restored lost lands and expanded his territory. He strengthened ties with Spain through marriage alliances. He chose not to get involved in the Seven Years War and instead focused on administrative reforms and maintaining a well-disciplined army.

Victor Amadeus I (Italian: Vittorio Amedeo I di Savoia; 8 May 1587 – 7 October 1637) was the Duke of Savoy and ruler of the Savoyard states from 26 July 1630 until his death in 1637. He was also known as the Lion of Susa.

He was succeeded by two of his sons; Francis Hyacinth and Charles Emmanuel II. His male-only line became extinct in 1831 with the death of Charles Felix. Therefore, the Kings of Italy are descended from his younger brother, Thomas Francis.