The Ukrainian Social Democratic Party was originally a Ukrainian section of the Polish-speaking Galician Social Democratic party by some ethnic-Ukrainian members of that part and leftist members of the Ukrainian Radical Party in Lviv. The key leaders were Mykola Hankevych (party chairman) and Semen Vityk. The party was based on the Ukrainian social democratic principles that were already in place by 1897. The first congress of the party took place in Lviv in 1903. In 1906, the party was amalgamated with its affiliate in Bukovina, the Social Democratic Party of Bukovina, under its leader, Yosyp Bezpalko.

The Ukrainian Social Democratic Party had close ties to the Ukrainian Social Democratic Labour Party in the Russian Empire.^[how?] Ideologically the party had an Austro-Marxist orientation.^{[citation needed]} It advocated the creation of an independent Ukrainian state.^{[contradictory]} V. Levynsky, Y. Bachynsky and Vityk Hankevych were leading personalities of the party.^[1] The party was active mobilizing for the 1902 peasant strikes in Husyatyn and Terebovlia counties. Until 1907 the party remained as a section of the Polish-dominated Galician party and Hankevych headed the Lviv city committee of the Social Democratic Party of Galicia.

In June 1907 the USDP has officially seceded from Galician Social Democratic Party at the party conference. The split allowed the USDP civil organization "Liberty" (Volya) to be more active in urban communities rather than to remain outside of cities.

In 1914 the party joined the Ukrainian General Council, and adopted a pro-Austrian position during the Great War.

Upon dissolution of the Austria-Hungary in 1918 and establishment of the Western Ukrainian People's Republic (ZUNR) the party became an independent Ukrainian party and joined the Ukrainian National Council (parliament of the ZUNR), but later left the coalition government creating the socialist opposition, the Peasants and Workers Union.

In 1921 the part switched to a pro-Soviet line advocating unification with Soviet Ukraine, while being hostile to the Polish government as well as the exiled government of Yevhen Petrushevych. Some Volhynian USDP members were elected to the National Sejm of Poland in 1922. By the early 1920s the party became infiltrated by members of the Communist Party of Western Ukraine and at its sixth Congress in Lviv in March 1923 it changed its political platform to Communist and removed its older leaders including Mykola Hankevych.

The Polish authorities outlawed the party on January 30, 1924, as one that caused a threat to peace and order. After the ban, many USDP cadres joined the underground faction of Communist Party of Western Ukraine.^[1] Other members who did not join the communists became involved in the Workers Community as a public cultural and educational society. In 1928, the party was revived by Lev Hankevych's "Forward" group (Vperid). In 1933 it joined the Labor and Socialist International and in December 1934 joined the Ukrainian Socialist Bloc that also included the Ukrainian National Democratic Alliance and the Ukrainian Socialist Radical Party.

• Social Democratic Party of Austria
• Polish Socialist Party

• Encyclopedia of Ukraine