Belarus–Ukraine relations
Belarus–Ukraine relations (, "Byelaruska-ŭkrainskiya adnosiny", , "Ukrains'ko-Bilorus'ki vidnosyny", , "Belorussko-ukrainskiye otnosheniya") are foreign relations between Belarus and Ukraine. Both countries were successively ruled by the Polish-Lithuanian Commonwealth, the Second Polish Republic, and ultimately, the Russian Empire. Prior to the 1991 breakup, both countries were part of the Soviet Union as the Belarusian SSR and Ukrainian SSR when they were the founding members of the United Nations in 1945. Being Slavic nations, both Belarus and Ukraine share closely related cultures and are predominantly inhabited by the East Slavic ethnic groups of Belarusians and Ukrainians respectively, along with a few Russians. Today, the two countries share an 891–km border.
Rusyns
Most of the predecessors of the Eastern Slavic inhabitants of present-day Western Ukraine, as well as of Western Belarus, referred to themselves as Ruthenians (Rusyns) (, transliteration "Rusyny") prior to the 19th century. Many of them became active participants in the creation of the Ukrainian nation and came to call themselves Ukrainians (Ukrainian: Українці, transliteration "Ukrayintsi"). There were, however, ethnic Rusyn enclaves, which were not a part of this movement: those living on the border of the same territory or in more isolated regions, such as the people from Carpathian Ruthenia, Poleshuks, or the Rusyns of Podlaskie. In the Soviet era, Boykos, Lemkos, Hutsuls, Rusyns, Ruski, Cossacks, Pinchuks, Polishchuks, and Lytvyns were classified as Ukrainian sub-groups.