The United Socialist Party (Partito Socialista Unitario, PSU) was a social-democratic

Social democracy

Social democracy is a political ideology of the center-left on the political spectrum. Social democracy is officially a form of evolutionary reformist socialism. It supports class collaboration as the course to achieve socialism...

 political party in Italy, active from 1922 to 1930.

The party was founded in November 1922 by the reformist

Reformism

Reformism is the belief that gradual democratic changes in a society can ultimately change a society's fundamental economic relations and political structures...

 wing of the Italian Socialist Party

Italian Socialist Party

The Italian Socialist Party was a socialist and later social-democratic political party in Italy founded in Genoa in 1892.Once the dominant leftist party in Italy, it was eclipsed in status by the Italian Communist Party following World War II...

 (PSI) led by Filippo Turati

Filippo Turati

Filippo Turati was an Italian sociologist, poet and Socialist politician.-Early life:Born in Canzo, province of Como, he graduated in law at the University of Bologna in 1877, and participated in the Scapigliatura movement with the most important artists of the period in Milan, publishing poetry...

 and Giacomo Matteotti

Giacomo Matteotti

Giacomo Matteotti was an Italian socialist politician. On 30 May 1924, he openly spoke in the Italian Parliament alleging the Fascists committed fraud in the recently held elections, and denounced the violence they used to gain votes...

, after they had been expelled in October. A staunch opponent of Benito Mussolini

Benito Mussolini

Benito Amilcare Andrea Mussolini was an Italian politician who led the National Fascist Party and is credited with being one of the key figures in the creation of Fascism....

 and Fascism

Italian Fascism

Italian Fascism also known as Fascism with a capital "F" refers to the original fascist ideology in Italy. This ideology is associated with the National Fascist Party which under Benito Mussolini ruled the Kingdom of Italy from 1922 until 1943, the Republican Fascist Party which ruled the Italian...

, Matteotti was assassinated by Fascist thugs, affiliated to Ceka, in June 1924. The event provoked the Aventine Secession). Outlawed in November 1925, the PSU became active in clandestinity, as the Italian Workers' Socialist Party (Partito Socialista dei Lavoratori Italiani, PSLI). In June 1930 the PSLI re-joined the PSI.

Leading members and activists of the party included Oddino Morgari

Oddino Morgari

Oddino Morgari was an Italian socialist journalist and politician.-Early life:Initially a Mazzinian radical, he became a member of the Italian Socialist Party in 1891, and was elected leader of its local section in Turin the following year...

, Sandro Pertini, Camillo Prampolini, Claudio Treves

Claudio Treves

Claudio Treves was an Italian politician and journalist.-Youth:Claudio Treves was born in Turin into a well off assimilated Jewish family...

 and Anna Kulischov.

The party was a member of the Labour and Socialist International

Labour and Socialist International

The Labour and Socialist International was an international organization of socialist and labour parties, active between 1923 and 1940. The LSI was a forerunner of the present-day Socialist International....

between 1923 and 1930.