After the outbreak of the First World War, the Second International declared bankruptcy. Lenin carried out a series of work to unite the revolutionary leftists of various countries and establish the Third International.

The victory of the Russian October Revolution, the development of the revolutionary movements in various countries, and the establishment of the Communist Parties in various countries further laid the foundation for the emergence of the Third International. From March 2 to 6, 1919, under the direct leadership of Lenin, an International Communist Conference was held in Moscow with representatives of the working-class parties of 30 countries. At the meeting, the Manifesto of the Communist International, the Programme of Action of the Communist International, and the Theses on Bourgeois Democracy and the Dictatorship of the Proletariat drafted by Lenin were adopted, proclaiming the establishment of the Third International.

The task of the Third International is to propagate Marxism, unite the working class and the broad masses of the working people in all countries, and fight for the overthrow of imperialist and capitalist rule, the establishment of the dictatorship of the proletariat, and the abolition of the system of exploitation. The Third International has criticized all kinds of opportunism, defended Marxism-Leninism, helped the vanguard of the working class in all countries to form revolutionary Marxist parties, helped the Communist Parties of various countries to train groups of capable cadres, supported the Soviet Union, the first socialist country in the world, supported the liberation movements of the oppressed nations in the Eastern countries, and waged a struggle against international fascism.

With the development of the international communist movement, starting from the principle of combining Marxism-Leninism with the specific practice of revolution in various countries, and considering that the original organizational form could no longer adapt to the requirements of the new situation, the Third International was officially dissolved in June 1943 with the unanimous consent of the Communist Parties of various countries.

In history, the Third International was also known as the Communist International.