The Socialist Party (Portuguese: Partido Socialista; pronounced [pɐɾˈtiðu susiɐˈliʃtɐ]) is a social-democratic[1] political party in Portugal. It was founded on 19 April 1973 in the German city of Bad Münstereifel, by militants from Portuguese Socialist Action (Portuguese: Acção Socialista Portuguesa)

José Sócrates, the current Prime Minister of Portugal, is the leader of the party. The party has currently 97 of 230 seats in the Portuguese Parliament. The Socialist Party stands out as about a third of its members in the Assembly of the Republic are women.

Sócrates obtained a landslide victory (winning 77% of the votes) in early October 2004 for the succession of Ferro Rodrigues as Secretary-General of the party. Other candidates for the post were Manuel Alegre and João Soares in a vote by party members.

PS is a member of the Socialist International and the Party of European Socialists, and has seven members in the European Parliament within the Socialists & Democrats (S&D) Group during the seventh parliament.