The Workers' Commissions (Spanish: Comisiones Obreras, CCOO) since the 1970s has become the largest trade union in Spain. It has more than one million members, and is the most successful union in labor elections, competing with the Unión General de Trabajadores (UGT) (historically affiliated with the Spanish Socialist Workers' Party (PSOE), and with the anarcho-syndicalist Confederación General del Trabajo (CGT), which is usually a distant third.

The CCOO were organized in the 1960s by the Communist Party of Spain (PCE) and workers' Roman Catholic groups to fight against Francoist Spain, and for labor rights (in opposition to the non-representative "vertical unions" in the Spanish Labour Organization). The various organizations formed a single entity after a 1976 Congress in Barcelona.

Along with other unions like the Unión Sindical Obrera (USO) and the UGT, it called a general strike in 1976, and carried out protests against the conditions in the country. Marcelino Camacho, a major figure of Spanish trade unionism and a PCE member, was CCOO's General Secretary from its foundation to 1985 - he was elected to the Congress of Deputies in the 1977 election. However, CCOO disassociated from the PCE in the early 1990s and is nowadays a non-partisan, negotiation-prone union.