The Organization of Ukrainian Nationalists (OUN) was a Ukrainian political organization created in 1929 in Vienna and acting in Western Ukraine (at the time interwar Poland). The OUN emerged as a union between the Ukrainian Military Organization, smaller radical right-wing groups, and right-wing Ukrainian nationalists and intellectuals represented by Dmytro Dontsov, Yevhen Konovalets, Mykola Stsyborsky and other figures.
In 1940, the OUN split into two parts. The older, pro-nazi members, supported Andriy Melnyk (OUN-M) while the younger antifascist and anticommunist members supported Stepan Bandera (OUN-B).

Members