The Popular Socialist Party (Spanish: Partido Popular Socialista, PPS) is a communist party in Mexico. It was founded in 1948 as the Popular Party (Partido Popular) by Vicente Lombardo Toledano.
Lombardo Toledano, the initial leader of the Confederation of Mexican Workers (CTM), decided to launch a new party in response to the increasingly moderate and corrupt policies of the ruling Institutional Revolutionary Party (PRI). The Popular Party was supported by the mine, oil and rail workers' unions, but its potential strength in elections was reduced by the strength of the PRI.
The party adopted Marxism-Leninism as its ideological line in 1960.
It was renamed the Popular Socialist Party in 1960, and over time its leadership became less critical of the PRI. In subsequent years it was often criticized as being a "loyal opposition," or part of the status quo. This led to a split by the PPS's left wing in the 1970s that formed the Party of the Mexican People (PPM), which merged with the Mexican Communist Party to form the Unified Socialist Party of Mexico (PSUM).
In 1997, a second party with nearly the same name (Popular Socialist Party of Mexico, or PPSM) split off from the older PPS. This splinter group claims to be the true descendant of Lombardo Toledano's party.
The PPS's traditional political space (i.e. to the left of the PRI) has largely been captured by the Party of the Democratic Revolution (PRD) since 1989. The PPS lost its registry as a national political party in 1997, though it is currently registered as a national political association under the name Popular Socialista.