International Workers' Unity – Fourth International (Spanish: Unidad Internacional de los Trabajadores – Cuarta Internacional) is a Trotskyist international organisation. It has members in Latin America, Western Europe and the CIS, including Izquierda Socialista in Argentina, Unidad Socialista de Izquierda in Venezuela, Corrente Socialista dos Trabalhadores in Brazil and Movimiento pelo Socialismo in Portugal.