Umberto II (Italian: Umberto Nicola Tommaso Giovanni Maria di Savoia; 15 September 1904 – 18 March 1983) was the last king of Italy. Umberto's reign lasted for 34 days, from 9 May 1946 until his formal deposition on 12 June 1946, although he had been the de facto head of state since 1944. Due to his short reign, he was nicknamed the May King (Italian: Re di maggio).

Umberto was the third child and only son among the five children of Victor Emmanuel III and Elena of Montenegro. As heir apparent to the throne, he received a customary military education and pursued a military career afterwards. In 1940, he commanded an army group during the brief Italian invasion of France shortly before the French capitulation. In 1942, he was promoted to Marshal of Italy but was otherwise inactive as an army commander during much of World War II. Umberto turned against the war following Italian defeats at Stalingrad and El Alamein, and tacitly supported the ouster of Benito Mussolini.

In 1944, Victor Emmanuel, compromised by his association with Italian fascism and desperate to repair the monarchy's image, transferred most of his powers to Umberto. He transferred his remaining powers to Umberto later in 1944 and named him Lieutenant General (Luogotenente) of the Realm; while retaining the title of King. As the country prepared for the 1946 Italian institutional referendum on the continuation of the Italian monarchy, Victor Emmanuel abdicated his throne in favour of Umberto, aspiring to bolster the monarchy with his exit. The June 1946 referendum saw voters voting to abolish the monarchy, and Italy was declared a republic days later. Umberto departed the country; he and other male members of the House of Savoy were barred from returning. He lived out the rest of his life in exile in Cascais, on the Portuguese Riviera. He died in Geneva Cantonal Hospital in 1983.

Umberto was born at the Castle of Racconigi in Piedmont. He was the third child and the only son of King Victor Emmanuel III of Italy and his wife, Jelena of Montenegro. As such, he was heir apparent from birth since the Italian throne was limited to male descendants. He was accorded the title Prince of Piedmont, which the Royal Decree formalised on 29 September 1904.

During the crisis of May 1915, when Victor Emmanuel III decided to break the terms of the Triple Alliance by declaring war on the Austro-Hungarian Empire, he found himself in a quandary as the Italian Parliament was against declaring war; several times, the king discussed abdication, with the throne to pass to the 2nd Duke of Aosta instead of Umberto. The British historian Denis Mack Smith wrote that it is not entirely clear why Victor Emmanuel was prepared to sacrifice his 10-year-old son's right to succeed to the throne in favour of the Duke of Aosta.

Umberto was brought up in an authoritarian and militaristic household and was expected to "show an exaggerated deference to his father"; both in private and public, Umberto always had to get down on his knees and kiss his father's hand before being allowed to speak, even as an adult, and he was expected to stand to attention and salute whenever his father entered a room. Umberto was given the formal military education of a Savoyard prince and like the other Savoyard princes before him, Umberto received an education that was notably short on politics; Savoyard monarchs customarily excluded politics from their heirs' education with the expectation that they would learn about the art of politics when they inherited the throne.

Umberto was the first cousin of King Alexander I of Yugoslavia. In a 1959 interview, Umberto told the Italian newspaper La Settimana Incom Illustrata that in 1922 his father had felt that appointing Benito Mussolini as prime minister was a "justifiable risk".

As Prince of Piedmont, Umberto visited South America, between July and September 1924. With his preceptor, Bonaldi, he went to Brazil, Uruguay, Argentina and Chile. This trip was part of the political plan of Fascism to link the Italian people living outside of Italy with their mother country and the interests of the regime. In Brazil, visits were scheduled to the national capital Rio de Janeiro and the State of São Paulo, where the largest Italian colony in the country lived. However, a major rebellion broke out on 5 July 1924, when Umberto had already departed from Europe, imposing a change in the Royal tour. The prince had to stop in Salvador, the capital of Bahia, to supply the ships, going directly to the other countries of South America. On his return, Umberto could only be received in Salvador again. Governor Góis Calmon, the Italian colony and other entities warmly welcomed the heir to the Italian Throne.