- The Union of Soviet Socialist Republics (USSR) was dissolved on 26 December 1991 by Declaration № 142-Н of the Soviet of the Republics of the Supreme Soviet of the Soviet Union, formally establishing the dissolution of the Soviet Union as a sovereign state and subject of international law. It also brought an end to the Soviet Union’s federal government and General Secretary (also President) Mikhail Gorbachev’s effort to reform the Soviet political and economic system in an attempt to stop a period of political stalemate and economic backslide.