The Soviet Union (USSR) officially collapsed on December 26, 1991. This followed the announcement of resignation by Mikhail Gorbachev as President of the Soviet Union on December 25, 1991, and the formal dissolution of the Union the next day into fifteen independent nation-states.
The collapse was the result of a rapid sequence of political events in 1991, including a failed coup attempt in August by Communist Party hardliners, rising nationalism among the republics, and the declaration of independence by several Soviet republics. The Supreme Soviet, which was the highest authority in the USSR, formally dissolved the Union in its final session on December 26.
Thus, the key date for the collapse of the USSR is December 26, 1991.
