Lithuanian Soviet Socialist Republic

The Lithuanian Soviet Socialist Republic (Lithuanian: Lietuvos Tarybų Socialistinė Respublika; Russian: Литовская Советская Социалистическая Республика, romanized: Litovskaya Sovetskaya Sotsialisticheskaya Respublika), also known as the Lithuanian SSR, Soviet Lithuania, or simply Lithuania, was de facto one of the constituent republics of the Soviet Union between 1940–1941 and 1944–1990. After 1946, its territory and borders mirrored those of today's Republic of Lithuania, with the exception of minor adjustments to its border with Belarus.

Source: Wikipedia — Lithuanian Soviet Socialist Republic (CC BY-SA 4.0)