In what year did the Soviet Union collapse?

It was a process extending over three years from 1989 to 1991.

The three Baltic Republic separated from the Union shortly after the collapse of the Berlin Wall. Shortly after a referendum among the 12 remaining republics indicated the general will to reform entirely the Union. Gorbachov resigned in 1991 and Yeltsin instituted a slack federal union among the newly independent sovereign 12 states.