Maoism or Mao Zedong Thought (Simplified Chinese: 毛泽东思想; pinyin: Máo Zédōng Sīxiǎng), is a variant of Marxism-Leninism derived from the teachings of the Chinese communist leader Mao Tse-tung.

It should be noted that the term Mao Zedong Thought has always been the preferred term by the Communist Party of China (CPC) and that the word Maoism has never been used in its English-language publications except pejoratively. Likewise, Maoist groups outside China have usually called themselves Marxist-Leninist rather than Maoist, a reflection of Mao's view that he did not change, but only developed, Marxism-Leninism. However, some Maoist groups, believing Mao's theories to have been sufficiently substantial additions to the basics of the Marxist canon, call themselves "Marxist-Leninist-Maoist" (MLM) or simply "Maoist."

In the People's Republic of China, Mao Zedong Thought is part of the official doctrine of the CCP, but since the 1978 beginning of Deng Xiaoping's market economy-oriented reforms, the concept of "socialism with Chinese characteristics" has come to the forefront of Chinese politics, Chinese economic reform has taken hold, and the official definition and role of Mao's original ideology in the PRC has been radically altered and reduced (see History of China). Outside the PRC, the term Maoism was used from the 1960s onwards, usually in a hostile sense, to describe parties or individuals who supported Mao Zedong and his form of communism. Since the death of Mao and the reforms of Deng, most of the parties explicitly defining themselves as "Maoist" have disappeared, but various communist groups around the world, particularly armed ones like the Communist Party of India (Maoist), the Communist Party of Nepal (Maoist) and the New People's Army of the Philippines, continue to advance Maoist ideas and get press attention for them. These groups generally have the idea that Mao's ideas were betrayed before they could be fully or properly implemented.

Maoism and its derivatives ardently support the pre-Nikita Khruschev-era Soviet Union and consider the developments of the Secret Speech to have begun that country's "revisionism" and "social-imperialism". It is usually accepted that Maoists follow an anti-revisionist and generally more militant political line than that of the "Peaceful coexistence" advanced by the Soviets and their followers after 1956. Traditionally most Maoists have deemed Joseph Stalin as the last true socialist leader of the Soviet Union.

Unlike the earlier forms of Marxism-Leninism in which the urban proletariat was seen as the main source of revolution, and the countryside was largely ignored, Mao focused on the peasantry as the main revolutionary force which, he said, could be led by the proletariat and its vanguard, the CCP. The model for this was the Chinese communist rural Protracted People's War of the 1920s and 1930s, which eventually brought the CCP to power. Furthermore, unlike other forms of Marxism-Leninism in which large-scale industrial development was seen as a positive force, Maoism made all-round rural development the priority. Mao felt that this strategy made sense during the early stages of socialism in a country in which most of the people were peasants. Unlike most other political ideologies, including other socialist and Marxist ones, Maoism contains an integral military doctrine and explicitly connects its political ideology with military strategy. In Maoist thought, "political power comes from the barrel of the gun" (one of Mao's quotes), and the peasantry can be mobilized to undertake a "people's war" of armed struggle involving guerrilla warfare in three stages.

The first stage involves mobilizing and organizing the peasantry. The second stage involves setting up rural base areas and increasing coordination among the guerrilla organizations. The third stage involves a transition to conventional warfare. Maoist military doctrine likens guerrilla fighters to fish swimming in a sea of peasants, who provide logistical support.

Maoism emphasizes "revolutionary mass mobilization" (physically mobilizing the vast majority of a population in the struggle for socialism), the concept of New Democracy, and the Theory of Productive Forces as applied to village-level industries independent of the outside world (see Great Leap Forward). In Maoism, deliberate organizing of massive military and economic power is necessary to defend the revolutionary area from outside threat, while centralization keeps corruption under supervision, amid strong control, and sometimes alteration, by the revolutionaries of the area's arts and sciences.

A key concept that distinguishes Maoism from most other left-wing ideologies (save for mainstream Marxism-Leninism) is the belief that the class struggle continues throughout the entire socialist period, as a result of the fundamental antagonistic contradiction between capitalism and communism. Even when the proletariat has seized state power through a socialist revolution, the potential remains for a bourgeoisie to restore capitalism. Indeed, Mao famously stated that "the bourgeoisie [in a socialist country] is right inside the Communist Party itself", implying that corrupt Party officials would subvert socialism if not prevented. This was officially the main reason for the Great Proletarian Cultural Revolution, in which Mao exhorted the public to "Bombard the [Party] headquarters!" and wrest control of the government from bureaucrats (such as Liu Shaoqi and Deng Xiaoping) perceived to be on the capitalist road.

Mao's doctrine is best summarized in the Little Red Book of Mao Zedong, which was distributed to everyone in China as the basis of revolutionary education. This book consists of quotations from the earliest days of the revolution to the mid-1960s, just before the beginning of the Cultural Revolution.