Communism (from Latin communis, 'common, universal') is a left-wing to far-left sociopolitical, philosophical, and economic ideology within the socialist movement, whose goal is the establishment of a communist society, a socioeconomic order centered around common ownership of the means of production, distribution, and exchange that allocates products to everyone in the society. Communist society also involves the absence of private property, social classes, money, and the state. Communists often seek a voluntary state of self-governance but disagree on the means to this end. This reflects a distinction between a more libertarian approach of communization, revolutionary spontaneity, and workers' self-management, and a more vanguardist or Communist party-driven approach through the development of a constitutional socialist state followed by the withering away of the state. As one of the main ideologies on the political spectrum, communism is placed on the left-wing alongside socialism, and communist parties and movements have been described as radical left or far left.

Variants of communism have been developed throughout history, including anarcho-communism, Marxist schools of thought, and religious communism, among others. Communism includes a variety of schools of thought, which broadly include Marxism, Leninism, and libertarian communism, as well as the political ideologies grouped around those. All of these different ideologies generally share the analysis that the current order of society stems from capitalism, its economic system, and mode of production, that in this system there are two major social classes, that the relationship between these two classes is exploitative, and that this situation can only ultimately be resolved through a social revolution. The two classes are the proletariat (the working class), who make up the majority of the population within society and must sell their labor to survive, and the bourgeoisie (the capitalist class), a small minority that derives profit from employing the working class through private ownership of the means of production. According to this analysis, a communist revolution would put the working class in power, and in turn establish common ownership of property, the primary element in the transformation of society towards a communist mode of production.

Communism in its modern form grew out of the socialist movement in 19th-century Europe, who blamed capitalism for the misery of urban factory workers. In the 20th century, several ostensibly Communist governments espousing Marxism–Leninism and its variants came into power, first in the Soviet Union with the Russian Revolution of 1917, and then in portions of Eastern Europe, Asia, and a few other regions after World War II. As one of the many types of socialism, communism became the dominant political tendency, along with social democracy, within the international socialist movement by the early 1920s. During most of the 20th century, around one-third of the world's population lived under Communist governments. These governments, which have been criticized by other leftists and socialists, were characterized by one-party rule and suppression of opposition and dissent. With the dissolution of the Soviet Union in 1991, several previously Communist governments repudiated or abolished Communist rule altogether. Afterwards, only a small number of nominally Communist governments remained, which are China, Cuba, Laos, North Korea, and Vietnam.

While the emergence of the Soviet Union as the world's first nominally Communist state led to communism's widespread association with the Soviet economic model, several scholars posit that in practice the model functioned as a form of state capitalism. Public memory of 20th-century Communist states has been described as a battleground between anti-anti-communism and anti-communism. Many authors have written about mass killings under communist regimes and mortality rates, such as excess mortality in the Soviet Union under Joseph Stalin, which remain a controversial, polarized, and debated topic in academia, historiography, and politics when discussing communism and the legacy of Communist states.