The Commonwealth of Independent States or CIS is made up of many, but not all, of the nations that previously formed the Soviet Union.
It does not involve the same level of coordination and cooperation seen across most of the European Union countries, but a certain level of economic and political collaboration between CIS states does exist. Its members are:
Ukraine was de facto participating in the Commonwealth until 2014 but was never an official member. Ukraine announced its withdrawal due to the Russian occupation of Crimea.