Umberto II of Italy in the context of "King Nicholas I of Montenegro"

King of Italy (Italian: Re d'Italia; Latin: Rex Italiae) was the title given to the ruler of the Kingdom of Italy after the fall of the Western Roman Empire. The first to take the title was Odoacer, a barbarian warlord, in the late 5th century, followed by the Ostrogothic kings up to the mid-6th century. With the Frankish conquest of Italy in the 8th century, the Carolingians assumed the title, which was maintained by subsequent Holy Roman Emperors throughout the Middle Ages. The last Emperor to claim the title was Charles V in the 16th century. During this period, the holders of the title were crowned with the Iron Crown of Lombardy.

A Kingdom of Italy was restored from 1805 to 1814 with Napoleon as its only king, centred in Northern Italy. It was not until the Italian unification in the 1860s that an independent Kingdom of Italy covering the entire Italian Peninsula was restored. From 1861 the House of Savoy held the title of King of Italy until the last king, Umberto II, was exiled in 1946 when Italy became a republic.

Nikola I Petrović-Njegoš (Serbian Cyrillic: Никола I Петровић-Његош; 7 October [O.S. 25 September] 1841 – 1 March 1921) was the last monarch of Montenegro from 1860 to 1918, reigning as prince from 1860 to 1910 and as the country's first and only king from 1910 to 1918. His grandsons were kings Alexander I of Yugoslavia and Umberto II of Italy, among others.

Alcide Amedeo Francesco De Gasperi (Italian: [alˈtʃiːde de ˈɡasperi]; 3 April 1881 – 19 August 1954) was an Italian politician and statesman who founded the Christian Democracy party and served as prime minister of Italy in eight successive coalition governments from 1945 to 1953.

De Gasperi was the last prime minister of the Kingdom of Italy, serving under both Victor Emmanuel III and Umberto II. He was also the first prime minister of the Italian Republic, and also briefly served as provisional head of state after the Italian people voted to end the monarchy and establish a republic. His eight-year term in office remains a landmark of political longevity for a leader in modern Italian politics. De Gasperi is the fifth longest-serving prime minister since the Risorgimento.

Queen of Italy (regina Italiae in Latin and regina d'Italia in Italian) is a title adopted by many spouses of the rulers of the Italian peninsula after the fall of the Roman Empire. The details of where and how the ruling kings ruled are in the article about them. The elective dignity of Roman Emperor was restricted to males only; therefore, there was never an Italian Queen regnant, though women such as Adelaide of Italy and Theophanu and Maria Theresa of Austria, who controlled the power of ruling, ruled as de facto Queens Regnant.

Paul-Henri Charles Spaak (French: [pɔl ɑ̃ʁi ʃaʁl spak]; 25 January 1899 – 31 July 1972) was an influential Belgian Socialist politician, diplomat and statesman who thrice served as the prime minister of Belgium and later as the second secretary general of NATO. Nicknamed "Mr. Europe", he was a leader in the formation of the institutions that evolved into the current European Union, along with Robert Schuman, Alcide De Gasperi and Konrad Adenauer.

A member of the influential Spaak family, he served briefly in World War I before he was captured, and rose to prominence after the war as a tennis player and lawyer, becoming famous for his high-profile defence of an Italian student accused of attempting to assassinate Italy's crown prince in 1929. A convinced socialist, Spaak entered politics in 1932 for the Belgian Workers' Party (later the Belgian Socialist Party) and gained his first ministerial portfolio in the government of Paul Van Zeeland in 1935.