The Soviet Union was primarily shaped by the ideologies of Marxism-Leninism, which was a variant of communism. It promoted the ideas of a classless society, collective ownership of the means of production, and the eventual establishment of a socialist state leading to communism. Additionally, the Soviet Union practiced state atheism and promoted the idea of a planned economy and the dictatorship of the proletariat under the leadership of the Communist Party. These ideologies played a significant role in shaping the policies and structure of the Soviet Union throughout its history.