The Socialist Party (Partito Socialista, PS) was a tiny social-democratic Italian political party. Its leader was Gianni De Michelis.
In June 2007 the New Italian Socialist Party split among those who wanted to participate to the foundation of the Socialist Party along with the Italian Democratic Socialists of Enrico Boselli, The Italian Socialists of Bobo Craxi and the Association for the Rose in the Fist of Lanfranco Turci and those who wanted to maintain the allegiance to the House of Freedoms coalition. The first group was led by Gianni De Michelis, the second one by Stefano Caldoro.
From July to October, the party had actually two secretaries, elected in two separate congresses: on 24 June Stefano Caldoro was elected secretary of the right-wing faction of the party, while on 7 July Mauro Del Bue replaced De Michelis as leader of those NPSI members who wanted to take part to the foundation of the Socialist Party, whose first meeting took place on 14 July 2007.
In October, after a consensual separation between the two groups and the foundation of the Socialist Party by Boselli, De Michelis, Craxi, Turci and splinters from Democratic Left (including Gavino Angius and Valdo Spini), the group of De Michelis changed name into "Socialist Party" (coherently with name of the future party). Subsequently the two MEPs of the party, De Michelis and Alessandro Battilocchio, joined the Socialist Group in the European Parliament.
In 2008, it joined five other minor social-democratic organisations to form the modern-day Italian Socialist Party.