Communist Party of the Soviet Union

The Communist Party of the Soviet Union (CPSU), also known at some points as the Russian Communist Party (Bolsheviks), the All-Union Communist Party (Bolsheviks), the Bolshevik Party, and the Soviet Communist Party, was the founding and ruling political party of the Soviet Union. The CPSU was the sole governing party of the Soviet Union until 1990 when the Congress of People's Deputies modified Article 6 of the 1977 Soviet Constitution, which had previously granted the CPSU a monopoly over the political system.

Source: Wikipedia — Communist Party of the Soviet Union (CC BY-SA 4.0)