political party and revolutionary movement that was founded in 1921 by revolutionaries such as Li Dazhao and Chen Duxiu who came out of the May Fourth Movement and who turned to Marxism after the victory of the Bolshevik Revolution (1917) in Russia. In the turmoil of 1920s China, CCP members such as Mao Zedong, Liu Shaoqi, and Li Lisan began organizing labour unions in the cities. The CCP joined with the Nationalist Party in 1924, and the alliance proved enormously successful at first. But after liberating Shanghai, the Nationalists under Chiang Kai-shek (Jiang Jieshi) turned violently on the CCP and drove it underground in 1927.

Many of the CCP cadres, such as Mao, then abandoned their revolutionary activities among China's urban proletariat and went to the countryside, where they were so successful in winning peasant support that in 1931 the Chinese Soviet Republic was set up in southern China with a population of 10,000,000. But this was destroyed by the military campaigns of the Nationalists, and Mao and the remnants of his forces escaped in the Long March (1934–35) to Yan'an in northern China. It was during this march that Mao achieved the leadership position in the CCP that he held until his death in 1976. Other important leaders who supported him in this period were Zhou Enlai and Zhu De.

In 1936 in the Xi'an (Sian) Incident (Xi'an Incident), Chiang Kai-shek was forced to call off his military campaigns against the CCP and instead enter a United Front with it against the Japanese invaders. While Chiang Kai-shek's Nationalist forces basically sat out the war in Chongqing, the CCP tremendously expanded its strength by fighting the Japanese invaders of China. By the end of the war it controlled base areas of some 100,000,000 people and had an experienced army and a workable political program of alliance between peasants, workers, the middle class, and small capitalists.

When the civil war recommenced in 1946, the CCP's land-reform program increased its peasant support while Nationalist ineptitude and demoralization cost it what little support it had. Decisively defeated, remnants of the Nationalists fled to Taiwan while the CCP and its allies founded the People's Republic of China in 1949.

After 1949 the life of the CCP was taken up with serious disagreements over the course of the country's development. At first the CCP adopted the Soviet model for development and closely allied itself with the Soviet Union. But the CCP and the Communist Party of the Soviet Union (CPSU) soon found themselves increasingly at odds over foreign policy and ideology, and, as the 1950s ended, the CCP and CPSU broke their close ties with each other. Internally the CCP attempted to hasten China's industrial development with bold but sometimes harmful programs such as the Great Leap Forward.

In 1966 Mao, who remained in serious disagreement with several other CCP leaders over the course of China's future economic and social development, launched the Cultural Revolution, and there followed a period of turbulent struggles between the CCP's radical wing under Mao and the more pragmatic wing led by Liu Shaoqi and Deng Xiaoping. Liu, Deng, and several other pragmatist leaders fell from power during the Cultural Revolution. An uneasy truce between radicals and pragmatists held from 1971 until 1976, when Zhou Enlai and Mao himself died. Almost immediately the radical group known as the Gang of Four, including Mao's widow, were arrested; and soon afterward the frequently purged and frequently rehabilitated Deng Xiaoping reappeared and assumed paramount power. The Cultural Revolution was formally ended, and the program of the “Four Modernizations” (of industry, agriculture, science/technology, and defense) was adopted. Restrictions on art and education were relaxed, and revolutionary ideology was deemphasized. After Mao's death Hua Guofeng was party chairman until 1981, when Deng's protege Hu Yaobang took over the post. Hu was replaced as the party general secretary (the post of chairman was abolished in 1982) by another Deng protégé, Zhao Ziyang, in 1987. Zhao was succeeded by Jiang Zemin in 1989, and Hu Jintao was elected general secretary in 2002.

With approximately 70,000,000 members by the end of 2005, the CCP is the largest political party in the world. It is a monolithic, monopolistic party that dominates the political life of China. It is the major policy-making body in China, and it sees that the central, provincial, and local organs of government carry out those policies.

The CCP's structure is as follows. Once every five years or so, a National Party Congress of some 2,000 delegates (the number varies) meets in plenary session to elect a Central Committee of about 200 full members, which in turn meets at least once a year. The Central Committee elects a Political Bureau of about 20–25 full members; this body is the ruling leadership of the CCP. The Political Bureau's Standing Committee of about six to nine of its most authoritative members is the highest leadership in the CCP and the country as a whole. In practice, power flows from the top down in the CCP.

The CCP's Secretariat is responsible for the day-to-day administrative affairs of the CCP. The general secretary of the Secretariat is formally the highest-ranking official of the party. The CCP has a commission for detecting and punishing abuses of office by party members, and it also has a commission by which it retains control over China's armed forces. The CCP has basic-level party organizations in cities, towns, villages, neighbourhoods, major workplaces, schools, and so on. The main publications of the CCP are the daily newspaper Renmin Ribao (“People's Daily”) and the biweekly theoretical journal Qiushi (“Seeking Truth”), which replaced the former monthly journal Hongqi (“Red Flag”) in 1988.