Republican Left of Catalonia in the context of "Catalan Countries"

The Popular Front (Spanish: Frente Popular) was an electoral alliance and pact formed in January 1936 to contest that year's general election by various left-wing political organizations during the Second Spanish Republic. The alliance was led by Manuel Azaña. In Catalonia and the modern-day Valencian Community, the coalition was known as the Front of the Lefts (Catalan: Front d'Esquerres).

The Popular Front included the Spanish Socialist Workers' Party (PSOE), Communist Party of Spain (PCE), and the republicans: Republican Left (IR), (led by Azaña) and Republican Union (UR), led by Diego Martínez Barrio. This pact was supported by Galician (PG) and Catalan nationalists (ERC), the POUM, socialist union Workers' General Union (UGT), and the anarchist trade union, the Confederación Nacional del Trabajo (CNT). Many anarchists who would later fight alongside Popular Front forces during the Spanish Civil War did not support them in the election, urging abstention instead.

Revolutionary Catalonia (21 July 1936 – 8 May 1937) was the period in which the autonomous region of Catalonia in northeast Spain was controlled or largely influenced by various anarchist, syndicalist, communist, and socialist trade unions, parties, and militias of the Spanish Civil War era. Although the constitutional Catalan institution of self-government, the Generalitat of Catalonia (led by the Republican Left of Catalonia, ERC), remained in power and even took control of most of the competences of the Spanish central government in its territory, the trade unions were de facto in command of most of the economy and military forces, which includes the Confederación Nacional del Trabajo (CNT, National Confederation of Labor) which was the dominant labor union at the time and the closely associated Federación Anarquista Ibérica (FAI, Iberian Anarchist Federation). The Unión General de Trabajadores (UGT, General Worker's Union), the POUM (Workers' Party of Marxist Unification) and the Unified Socialist Party of Catalonia (PSUC, which included the former Communist Party of Catalonia) were also prominent.

Socialist rule of the region began with the Spanish Revolution of 1936, resulting in workers' control of businesses and factories, collective farming in most of the countryside, and attacks against Spanish nationalists and the Catholic clergy. The growing influence of the Communist Party of Spain (PCE) in the Popular Front government and their desire to nationalize revolutionary committees and militias brought it into conflict with the CNT and POUM, resulting in the May Days and the eventual replacement of the CNT by the PSUC as a major political force in Catalonia until their defeat to the Nationalist forces in 1939.