Bulgarian Social Democratic Party (1891)

The Bulgarian Social Democratic Party (BSDP) was the first socialist party established in Bulgaria. Founded on August 2, 1891, at a congress held on Mount Buzludzha, the party emerged from earlier socialist circles and organizations that had been active in the country during the late 19th century.

Key figures in the party's early development included Dimitar Blagoev, considered the founder and primary ideologue, as well as Nikola Gabrovski, Georgi Kirkov, and Christian Rakovski (though the latter later became more active in Romanian politics). The BSDP's initial program advocated for the improvement of working conditions, universal suffrage, and the nationalization of certain industries, drawing inspiration from Marxist principles.

Early on, the BSDP faced internal divisions regarding its strategy and ideology. A major split occurred in 1903 at the party's Tenth Congress. One faction, led by Dimitar Blagoev, became known as the "Narrow Socialists" (Tesni Sotsialisti). They adhered to a more orthodox Marxist line, emphasizing revolutionary struggle and proletarian internationalism. The other faction, known as the "Broad Socialists" (Shiroki Sotsialisti), favored a more gradualist approach, advocating for reform through parliamentary means and cooperation with other political forces.

The Narrow Socialists eventually evolved into the Bulgarian Communist Party (BCP) in 1919, which came to dominate Bulgarian politics after World War II. The Broad Socialists, after several reorganizations and changes in name, continued to exist as a separate socialist party, playing a role in Bulgarian politics particularly during periods of democratic opening. The legacy of the BSDP and its subsequent factions significantly shaped the political landscape of Bulgaria throughout the 20th century.