The
Byelorussian Soviet Socialist Republic (
Byelorussian SSR or
BSSR;
Bielaruskaja Savieckaja Sacyjalistycnaja Respublika, Bielaruskaja SSR;
Belorusskaya Sovetskaya Sotsialisticheskaya Respublika, Belorusskaya SSR), also referred to as
Byelorussia, was one of
fifteen constituent republics of the
Soviet Union (USSR). To the west it bordered
Poland. Within the USSR, it bordered the
Lithuanian and
Latvian SSRs to the north, the
Russian SFSR to the east and the
Ukrainian SSR to the south.