Unified PSI–PSDI

The Unified PSI–PSDI (PSI–PSDI Unificati) was the name of the federation of parties formed by the Italian Socialist Party (PSI) and the Italian Democratic Socialist Party (PSDI) from 1966 to 1969. The federal party was often unofficially referred to as the Unified Socialist Party (Partito Socialista Unificato).

The two parties joined forces in 1966, after the entrance of PSI for the first time in an Italian government majority, the centre-left coalition led by Aldo Moro and composed of Christian Democracy, Italian Republican Party and PSDI. The membership was 700,964 activists.^[1]

After the unsuccessful performance of the united party in the 1968 general election, the PSi-PSDI returned officially to the name PSI. On July 6, 1969, the former members of PSDI left to form the "United Socialist Party", which adopted back the denomination of PSDI in 1971.

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Historical Italian political parties (current parties)

Communist	Communist Party of Italy, Italian Communist Party, Organisation of Communists of Italy (Marxist-Leninists), Proletarian Unity Party, Proletarian Democracy, Movement of Unitarian Communists

Socialist and social-democratic	Italian Revolutionary Socialist Party, Italian Labour Party, Italian Socialist Party, Independent Socialist Party, Italian Reform Socialist Party, United Socialist Party (1922), Social Christian Party, United Socialist Party (1949), Italian Democratic Socialist Party, Unified Socialist Party, Italian Socialist Party of Proletarian Unity, Democratic Party of the Left/Democrats of the Left, Italian Socialists/Italian Democratic Socialists

Green	Green Lists, Rainbow Greens

Social-liberal	Radical Party (1877), Constitutional Democratic Party, Democratic Liberal Party, Reform Democratic Party, Italian Social Democratic Party, Italian Republican Party, Party of Italian Peasants, Action Party, Labour Democratic Party, Republican Democratic Concentration, Community Movement, Radical Party (1955), Democratic Alliance, Democratic Union, Movement for Democracy – The Net, The Democrats, European Republicans Movement

Centrist	Patto Segni, Italian Renewal, United Consumers, Southern Democratic Party, Middle-of-the-Road Italy, Democracy is Freedom – The Daisy

Christian-democratic	Italian People's Party (1919), Christian Democracy, Italian People's Party (1994), Christian Democratic Centre, United Christian Democrats, Christian Democrats for the Republic, Democratic Union for the Republic, European Democracy

Conservative-liberal	Italian Liberal Party, Italian Unionist Movement, National Democratic Alliance, Union of the Centre, Forza Italia, Liberal Party

Conservative	Party of Combatants, Economic Party, Front of the Ordinary Man, Monarchist National Party, People's Monarchist Party, Italian Democratic Party of Monarchist Unity, National Democracy, National Alliance

Fascist and post-fascist	National Fascist Party, Republican Fascist Party, Italian Social Movement, National Front, National Social Front, National Vanguard

Coalitions	Leftist coalitions: Popular Democratic Front, Alliance of Progressives, The Left – The Rainbow Centre-left coalitions: Socialist Unity, The Olive Tree, The Sunflower, The Union, Rose in the Fist Centrist coalitions: Pact for Italy, Pact of Democrats Centre-right coalitions: National Democratic Union, National Bloc, Pole of Freedoms, Pole of Good Government, House of Freedoms Rightist coalitions: National Bloc of Freedom Neo-fascist coalitions: Social Alternative