The Yan'an Rectification Movement (simplified Chinese: ; traditional Chinese: ; pinyin: Yn'n Zhngfng Yndng), also known as Zhengfeng or Cheng Feng, was the first ideological mass movement initiated by the Chinese Communist Party (CCP), going from 1942 to 1945. The movement took place at the communist base at Yan'an, a remote and isolated mountainous area in northern Shaanxi, after the communists' Long March. Though it was during the Second Sino-Japanese War, the CCP was experiencing a time of relative peace when they could focus on internal affairs.The legacies of the Yan'an era proved fundamental to the subsequent history of the Chinese Communist Party, according to Kenneth Lieberthal. These included the consolidation of Mao Zedong's paramount role within the CCP, especially from 1942 to 1944, and the adoption of a party constitution that endorsed Marxist-Leninism and Mao Zedong Thought as guiding ideologies. This move formalised Mao's deviation from the Moscow party line and the importance of Mao's alleged 'adaptation of communism to the conditions of China'. The Rectification Campaign was successful in either convincing or coercing the other leaders of the CCP to support Mao. Because the CCP had overcome great odds to grow and develop during this period, the methods employed in Yan'an were looked upon in reverence during Mao's later years. After the founding of the People's Republic of China in 1949, Mao repeatedly used some of the tactics that had been successful in Yan'an whenever he felt the need to monopolize political power. To a large extent, the Yan'an Rectification Campaign began with the "systematic remolding of human minds."More than 10,000 were killed in the "rectification" process, as the CCP made efforts to attack intellectuals and replace the culture of the May Fourth Movement with that of Communist culture. The rectification movement is regarded by many as the origin of Mao Zedong's cult of personality.

Mao Zedong (December 26, 1893 – September 9, 1976), also known as Chairman Mao, was a Chinese communist revolutionary who was the founder of the People's Republic of China (PRC), which he ruled as the chairman of the Chinese Communist Party from the establishment of the PRC in 1949 until his death in 1976. Ideologically a Marxist–Leninist, his theories, military strategies, and political policies are collectively known as Maoism.

Mao was the son of a prosperous peasant in Shaoshan, Hunan. He supported Chinese nationalism and had an anti-imperialist outlook early in his life, and was particularly influenced by the events of the Xinhai Revolution of 1911 and May Fourth Movement of 1919. He later adopted Marxism–Leninism while working at Peking University as a librarian and became a founding member of the Chinese Communist Party (CCP), leading the Autumn Harvest Uprising in 1927. During the Chinese Civil War between the Kuomintang (KMT) and the CCP, Mao helped to found the Chinese Workers' and Peasants' Red Army, led the Jiangxi Soviet's radical land policies, and ultimately became head of the CCP during the Long March. Although the CCP temporarily allied with the KMT under the Second United Front during the Second Sino-Japanese War (1937–1945), China's civil war resumed after Japan's surrender, and Mao's forces defeated the Nationalist government, which withdrew to Taiwan in 1949.

On October 1, 1949, Mao proclaimed the foundation of the PRC, a Marxist–Leninist single-party state controlled by the CCP. In the following years he solidified his control through the Chinese Land Reform against landlords, the Campaign to Suppress Counterrevolutionaries, the "Three-anti and Five-anti Campaigns", and through a psychological victory in the Korean War, which altogether resulted in the deaths of several million Chinese. From 1953 to 1958, Mao played an important role in enforcing planned economy in China, constructing the first Constitution of the PRC, launching the industrialisation program, and initiating military projects such as the "Two Bombs, One Satellite" project and Project 523. His foreign policies during this time were dominated by the Sino-Soviet split which drove a wedge between China and the Soviet Union. In 1955, Mao launched the Sufan movement, and in 1957 he launched the Anti-Rightist Campaign, in which at least 550,000 people, mostly intellectuals and dissidents, were persecuted. In 1958, he launched the Great Leap Forward that aimed to rapidly transform China's economy from agrarian to industrial, which led to the deadliest famine in history and the deaths of 15–55 million people between 1958 and 1962. In 1963, Mao launched the Socialist Education Movement, and in 1966 he initiated the Cultural Revolution, a program to remove "counter-revolutionary" elements in Chinese society which lasted 10 years and was marked by violent class struggle, widespread destruction of cultural artifacts, and an unprecedented elevation of Mao's cult of personality. Tens of millions of people were persecuted during the Revolution, while the estimated number of deaths ranges from hundreds of thousands to millions. After years of ill health, Mao suffered a series of heart attacks in 1976 and died at the age of 82. During Mao's era, China's population grew from around 550 million to over 900 million while the government did not strictly enforce its family planning policy.

A controversial figure within and outside China, Mao is still regarded as one of the most important individuals in the twentieth century. Beyond politics, Mao is also known as a theorist, military strategist, and poet. During the Mao era, China was heavily involved with other southeast Asian communist conflicts such as the Korean War, the Vietnam War, and the Cambodian Civil War, which brought the Khmer Rouge to power. He ruled China through an autocratic and totalitarian regime responsible for mass repression as well as destruction of religious and cultural artifacts and sites. The government was responsible for vast numbers of deaths with estimates ranging from 40 to 80 million victims through starvation, persecution, prison labour, and mass executions. Mao has been praised for transforming China from a semi-colony to a leading world power, with greatly advanced literacy, women's rights, basic healthcare, primary education and life expectancy.