A communist party is a political party that seeks to realize the socio-economic goals of communism. The term "communist party" was popularized by the title of The Manifesto of the Communist Party (1848) by Karl Marx and Friedrich Engels. As a vanguard party, the communist party guides the political education and development of the working class (proletariat). As a ruling party, the communist party exercises power through the dictatorship of the proletariat. Vladimir Lenin developed the idea of the communist party as the revolutionary vanguard, when the socialist movement in Imperial Russia was divided into ideologically opposed factions, the Bolshevik faction ("of the majority") and the Menshevik faction ("of the minority"). To be politically effective, Lenin proposed a small vanguard party managed with democratic centralism which allowed the centralized command of a disciplined cadre of professional revolutionaries. Once a policy was agreed upon, realizing political goals required every Bolshevik's total commitment to the agreed-upon policy.

In contrast, the Menshevik faction, which initially included Leon Trotsky, emphasized that the party should not neglect the importance of mass populations in realizing a communist revolution. In the course of the revolution, the Bolshevik party which became the Communist Party of the Soviet Union (CPSU) assumed government power in Russia after the October Revolution in 1917. With the creation of the Communist International (Comintern) in 1919, the concept of communist party leadership was adopted by many revolutionary parties, worldwide. In an effort to standardize the international communist movement ideologically and maintain central control of the member parties, the Comintern required that its members use the term "communist party" in their names.

Under the leadership of the CPSU, the interpretations of orthodox Marxism were applied to Russia and led to the emergence of Leninist and Marxist–Leninist political parties throughout the world. After the death of Lenin, the Comintern's official interpretation of Leninism was the book Foundations of Leninism (1924) by Joseph Stalin.

As the membership of a communist party was to be limited to active cadres in Lenin's theory, there was a need for networks of separate organizations to mobilize mass support for the party. Typically, communist parties built up various front organizations whose membership was often open to non-communists. In many countries, the single most important front organization of the communist parties was its youth wing. During the time of the Communist International, the youth leagues were explicit communist organizations, using the name 'Young Communist League'. Later the youth league concept was broadened in many countries, and names like 'Democratic Youth League' were adopted.

Some trade unions and students', women's, peasants', and cultural organizations have been connected to communist parties. Traditionally, these mass organizations were often politically subordinated to the political leadership of the party. After the fall of communist party regimes in the 1990s, mass organizations sometimes outlived their communist party founders.

At the international level, the Communist International organized various international front organizations (linking national mass organizations with each other), such as the Young Communist International, Profintern, Krestintern, International Red Aid, Sportintern, etc. Many of these organizations were disbanded after the dissolution of the Communist International. After the Second World War new international coordination bodies were created, such as the World Federation of Democratic Youth, International Union of Students, World Federation of Trade Unions, Women's International Democratic Federation and the World Peace Council. The Soviet Union unified many of the Comintern's original goals in the Eastern Bloc under the aegis of a new organization, the Cominform.

Historically, in countries where communist parties were struggling to attain state power, the formation of wartime alliances with non-communist parties and wartime groups was enacted (such as the National Liberation Front of Albania). Upon attaining state power these Fronts were often transformed into nominal (and usually electoral) "National" or "Fatherland" Fronts in which non-communist parties and organizations were given token representation (a practice known as Blockpartei), the most popular examples of these being the National Front of East Germany (as a historical example) and the North Korean Reunification Front (as a modern-day example). Other times the formation of such Fronts was undertaken without the participation of other parties, such as the Socialist Alliance of Working People of Yugoslavia and the National Front of Afghanistan, though the purpose was the same: to promote the communist party line to generally non-communist audiences and to mobilize them to carry out tasks within the country under the aegis of the Front.^{[citation needed]}

Recent scholarship has developed the comparative political study of global communist parties by examining similarities and differences across historical geographies. In particular, the rise of revolutionary parties, their spread internationally, the appearance of charismatic revolutionary leaders and their ultimate demise during the decline and fall of communist parties worldwide have all been the subject of investigation.