The Revolutionary Socialist Party (Portuguese: Partido Socialista Revolucionário, pronounced [pɐɾˈtiðu susiɐˈliʃtɐ ʁɨvulusiuˈnaɾiu], or PSR) was a left-wing party in Portugal, founded in 1978 after the merger of two Trotskyist parties: the Internationalist Communist League (Portuguese: Liga Comunista Internacionalista LCI) and the Workers Revolutionary Party (Portuguese: Partido Revolucionário dos Trabalhadores, PRT).

The original party, a member of the Fourth International, was however officially dissolved in 2008.

In 1985, after some splits, the Party gained a new life, mainly due to its anti-militaristic and anti-racist campaigns and in that year's election, the PSR got 0.6% of the vote.

[4] Also in 1987, the Party started publishing of the Combate (Struggle) monthly newspaper.

[7] In 1998, the party formed a permanent coalition with the People's Democratic Union, the Politics XXI and the Left Revolutionary Front, creating the Bloco de Esquerda (Left Bloc).