The Workers' Socialist Movement (Spanish: Movimiento Socialista de los Trabajadores, MST) is a Trotskyist political party in Argentina. The MST was founded in 1992 as a split from another Trotskyist group, the Movement Towards Socialism (see Nahuel Moreno). The MST is active on a number of college campuses, including the University of Buenos Aires. In 2006, the party has suffered a crisis, which led to a split. The minority founded a new organization, named Socialist Left.
Leading members include Cele Fierro and Alejandro Bodart.
Internationally, it is affiliated to the International Socialist League (2019).