The Socialist Party (Portuguese: Partido Socialista; pronounced: [pɐɾˈtiðu susiɐˈliʃtɐ]), abbreviated to PS, is a social-democratic 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).

The current leader is António José Seguro. José Sócrates, the former Prime Minister of Portugal, was the leader of the leader of the party until 5 June 2011. The party has currently 74 of 230 seats in the Portuguese Parliament and lost the June 2011 election. The Socialist Party stands out as about a third of its members in the Assembly of the Republic are women.^{[citation needed]}

Sócrates resigned as General Secretary on election night of 5 June 2011, due to having lost the general election by a margin higher than expected. Seguro was elected as leader of the party on July 23, winning 68% of the vote against his challenger, Francisco Assis, who got 32%.