Lithuanian-Byelorussian Soviet Socialist Republic (LBSSR, Litbel) existed within the territories of modern Belarus and Lithuania for a brief period within 1919, before the area has been annexed to Poland.

In December 1918 the Germans left the land, and on January 2, 1919 the Byelorussian Soviet Socialist Republic was declared, which was joined with the Lithuanian SSR into the LBSSR on February 27, 1919.

The leaders of the state were Kazimir Tsikhovsky (Kazimierz Cichowski , Казимир Генрихович Циховский), Chairman of the Central Executive Committee of the Congress of Soviets (corresponds to head of parliament) and Vincas Mickevicius-Kapsukas (Винцас Симанович Мицкявичюс-Капсукас), Chairman of the Sovnarkom (corresponds to prime minister).

Its capital was initially Vilnius. In April it was moved to Minsk, when Vilnius was seized by the Polish Army with the onset of the Polish-Soviet War, and then to Smolensk, in August 1919.

BLSSR was dissolved on August 25, 1919, when the whole territory was controlled by armies of Poland, Entente, Letuvos Taryba of Antanas Smetona, and Germany.

In 1920, the lands of Belarus were annexed to Poland and Byelorussian Soviet Socialist Republic.