Amadeus I (Amadeo) (May 30, 1845 - January 18, 1890), Duke of Aosta and King of Spain, was born in Turin, Italy. He was the second son of Victor Emmanuel II (King of Piedmont, Savoy, Sardinia and, later, first King of Italy) and Mary Adelaide of Austria.

In 1867, he married Maria Victoria dal Pozzo della Cisterna. One year later, after the Spanish revolution, the new courts decided to reinstate a monarchy. Amadeus I was elected King after Isabella II was dethroned.

Thanks to the backing of the Carlist movement, Amadeus was elected King on November 16, 1870. He swore to uphold the constitution in Madrid on January 2, 1871.

The election of the new King coincided with the assassination of General Juan Prim, his main backer. After that, Amadeus had to deal with difficult situations, with unstable Spanish politics, republican conspiracies, Carlist uprisings, separatism in Cuba, same-party disputes, fugitive governments and assassination attempts.

He could only count on the support of the progressive party, whose leaders were trading off in the government thanks to parliamentary majority and electoral fraud. The progressives divided into monarchists and constitutionalists, which made the instability worse, and in 1872 a violent outburst of interparty conflicts hit a peak. The Carlists uprose in the Basque and Catalan regions, and after that, republican uprisings happened in various cities dispersed across the country.

With the possibility of reigning with no popular support, Amadeus abdicated from the Spanish throne on February 11, 1873. At ten o'clock that same night, Spain was proclaimed a republic, at which Amadeus made an appearance before the courts, proclaiming the Spanish people ungovernable.

Completely disgusted, the ex-monarch left Spain to go back to Italy, where he took over the title of Duke of Aosta. There he stayed until he died.

He was succeeded in 1875 by Alfonso XII, the son of Isabella II. After a brief regency of Antonio Cánovas del Castill, Spanish prime minister from 1873 until his assassination in 1893.

Preceded by:
Isabella II of Spain
List of Spanish monarchs Succeeded by the
First Spanish Republic,
and then
Alfonso XII of Spain