Congress of the Communist Party of the Soviet Union
The Congress of the Communist Party of the Soviet Union (Russian: Съезд Коммунистической партии Советского Союза, romanized: S"ezd Kommunisticheskoy partii Sovetskovo Soyuza) was the supreme decision-making body of the Communist Party of the Soviet Union. Its meetings served as convention of all party delegates and their predecessors.
Source: Wikipedia — Congress of the Communist Party of the Soviet Union (CC BY-SA 4.0)