The House of Savoy (Italian: Casa Savoia) was formed in the early 11th century in the historical Savoy region. Through gradual expansion, it grew from ruling a small county in that region to eventually rule the Kingdom of Italy from 1861 until the end of World War II. The House of Savoy ruled unified Italy for 85 years with Victor Emmanuel II, Umberto I, Victor Emmanuel III, and Umberto II as monarchs. The last monarch ruled for a few weeks before being overthrown by a popular referendum and a new republican government.

The House of Savoy emerged, along with the free communes of Switzerland, in what is now called Switzerland. The name derives from the historical region Savoy in what is now France and Italy. Over time the house expanded from that region to rule almost all of the Italian Peninsula. Yet their growth and survival over the centuries was not based on spectacular conquests, but on gradual territorial expansion through marriage and methodical and highly manipulative political acquisitions.

Savoy (/ˈsævɔɪ/; Arpitan: Savouè, IPA: [saˈvwɛ]; French: Savoie, IPA: [savwa]; Italian: Savoia) is a region of France. It comprises roughly the territory of the Western Alps situated between Lake Geneva in the north and Dauphiné in the south.

The historical land of Savoy emerged as the feudal territory of the house of Savoy during the 11th to 14th centuries. The historical territory is shared between the modern republics of France and Italy.

Installed by Rudolph III, King of Burgundy, officially in 1003, the House of Savoy became the longest surviving royal house in Europe.^{[citation needed]} It ruled the County of Savoy to 1416 and then the Duchy of Savoy from 1416 to 1714.

The territory of Savoy was annexed to France in 1792 under the French First Republic, before being returned to the Kingdom of Piedmont-Sardinia in 1815. Savoy was finally annexed to France, under the Second French Empire in 1860, as part of a political agreement brokered between the French emperor Napoleon III and King Victor Emmanuel II of the Kingdom of Sardinia that began the process of unification of Italy. Victor Emmanuel's dynasty, the House of Savoy, retained its Italian lands of Piedmont and Liguria and became the ruling dynasty of Italy.