When one thinks of the USSR or SOVIET UNION...you generally think of this flag...
However...each individual republic had it's own flag...
First, I have added a bit of general info...before we look into each Republic.
The Republics of the Soviet Union or the Union Republics (Russian: союзные республики, soyuznye respubliki) of the Soviet Union were ethnically based administrative units that were subordinated directly to the Government of the Soviet Union.
In the final decades of its existence, the Soviet Union officially consisted of fifteen Soviet Socialist Republics (SSR). All of them were considered to be Soviet socialist republics (SSRs), and all of them, with the exception of the Russian SFSR, had their own Communist parties, part of the Communist Party of the Soviet Union.
However, the Baltic countries, Lithuania, Latvia, and Estonia, do not consider themselves to have ever been part of the USSR. They assert that their incorporation into the Soviet Union in 1940 (as the Lithuanian SSR, Latvian SSR, and Estonian SSR) under the provisions of the 1939 Molotov-Ribbentrop Pact was illegal, and that they therefore remained independent countries under Soviet occupation. Their position is supported by the European Court of Human Rights, the United Nations Human Rights Council, the United States, and the European Union. In contrast, the Russian government and state officials maintain that the Soviet annexation of the Baltic states was legitimate.
All of the former Republics are now independent countries, with eleven of them (all except the Baltic states and Georgia) being very loosely organized under the heading of the Commonwealth of Independent States.
Each republic had its own unique set of state symbols: a flag, a coat of arms, and, with the exception of the Russian SFSR, an anthem. Every republic of the Soviet Union also was awarded with the Order of Lenin. Two (Ukraine and Belarus) were members of the United Nations General Assembly.