Umberto I (Italian: Umberto Ranieri Carlo Emanuele Giovanni Maria Ferdinando Eugenio di Savoia; 14 March 1844 – 29 July 1900) was King of Italy from 9 January 1878 until his assassination in 1900. His reign saw the creation of the Italian Empire, as well as the creation of the Triple Alliance among Italy, Germany, and Austria-Hungary.

The son of Victor Emmanuel II and Adelaide of Austria, Umberto took part in the Italian Wars of Independence as a commander of the Royal Sardinian Army. He assumed the Italian throne in 1878 on the death of his father. A strong militarist, Umberto approved the alliance with Germany and Austria-Hungary, which was formalised in 1882. He also encouraged Italy's colonial efforts and oversaw the incorporation of Eritrea and Somalia into the Italian Empire.

Domestically, Umberto faced increasing social unrest and serious economic difficulties. Tensions mounted as a result of public opposition to Italy's colonial wars, the spread of socialist ideas, and crackdowns on civil liberties. He was deeply loathed in left-wing circles for his conservatism and his support of the Bava Beccaris massacre in Milan, in which demonstrations over rising food prices were bloodily suppressed by the military. He was particularly hated by Italian anarchists, who attempted to assassinate him during the first year of his reign.

In 1900, two years after the Bava Beccaris massacre, Umberto was killed in Monza by Italian-American anarchist Gaetano Bresci. He was succeeded by his son, Victor Emmanuel III. Before his killing, he was also one of the recipients of one of Friedrich Nietzsche's Wahnbriefe notes. The Umbertino architecture style was named after him.

The son of Victor Emmanuel II and Archduchess Adelaide of Austria, Umberto was born in Turin, which was then capital of the Kingdom of Piedmont-Sardinia, on 14 March 1844, his father's 24th birthday. His education was entrusted to, among others, Massimo Taparelli, Marquess d'Azeglio, and Pasquale Stanislao Mancini. As Crown Prince, Umberto was distrusted by his father, who gave him no training in politics or constitutional government. Umberto was brought up with no affection or love. Instead, Umberto was taught to be obedient and loyal; he had to stand at attention whenever his father entered the room. When speaking to his father, Umberto had to get down on his knees to kiss his father's hand first. The fact that Umberto had to kiss his father's hand before being allowed to speak to him (both in public and in private) right up to his father's death contributed much to the tension between the two.

From March 1858, he had a military career in the Royal Sardinian Army, beginning with the rank of captain. Umberto took part in the Italian Wars of Independence. In the Second War of Italian Independence (1859), Umberto, who was only 14, was present at the battle of Solferino. In the Third War of Italian Independence (1866), Umberto commanded the XVI Division at the Villafranca battle that followed the Italian defeat at Custoza.

Because of the upheaval the House of Savoy caused to a number of other royal houses (all the Italian ones, and those related closely to them, such as the Bourbons of Spain and France) in 1859–60, only a minority of royal families in the 1860s were willing to establish relations with the newly founded Italian royal family. It proved difficult to find any royal bride for either of the sons of king Victor Emmanuel II (his younger son Amedeo, Umberto's brother, married a Piedmontese subject, princess Vittoria of Cisterna). Their conflict with the papacy did not help these matters. Not many eligible Catholic royal brides were easily available for young Umberto.^{[citation needed]}

At first, Umberto was to marry Archduchess Mathilde of Austria, a scion of a remote sideline of the Austrian imperial house; however, she died as the result of an accident at the age of 18. On 21 April 1868, Umberto married his first cousin, Margherita Teresa Giovanna, Princess of Savoy. Their only son was Victor Emmanuel, prince of Naples. While Umberto was to be described by a modern historian as "a colourless and physically unimpressive man, of limited intellect", Margherita's appearance, cultural interests and strong personality were to enhance the popularity of the monarchy. Umberto kept many mistresses on the side, and his favourite mistress, Eugenia, the wife of Duke Litta Visconti-Arese, lived with him at his court as his common-law wife. He forced Queen Margherita to accept Eugenia as a lady-in-waiting.