The Puerto Rican Socialist Party (Spanish: Partido Socialista Puertorriqueño, PSP) was a Marxist and pro-independence political party in Puerto Rico seeking the end of United States of America control on the Hispanic and Caribbean island of Puerto Rico. It proposed a "democratic workers' republic".
The PSP originated as the Movimiento Pro-Independencia (MPI), founded on January 11, 1959, in the city of Mayagüez. The MPI was formed by a group of dissidents from the Puerto Rican Independence Party (PIP), former militants of the Nationalist Party of Puerto Rico and the Communist Party of Puerto Rico, and university students, some of them members of the Federación de Universitarios Pro Independencia (FUPI). The MPI was greatly influenced by the Cuban Revolution.
During the 1964 and 1968 elections, and the 1967 plebiscite on the political status of Puerto Rico, the MPI promoted a boycott. Throughout the decade the MPI campaigned against the presence of big US corporations denouncing they hindered the island's development, destroyed native industries and agriculture, and exploited the workers. The MPI gathered sympathies among students, workers, intellectuals and poor communities, and advocated civil disobedience and resistance. Opposition amongst the youth and students to compulsory military service in the US Army (in which Puerto Ricans had to serve since 1917); to the presence of the ROTC at the University of Puerto Rico; to US aggressive military policies in the Caribbean, Latin America, Southeast Asia and elsewhere; an to American military installations on the island fueled the activity of the MPI and this in its turn created a perspective of a possible decolonization.