Vanguardism, a core concept of Leninism, is the idea that a revolutionary vanguard party, composed of the most conscious and disciplined workers, must lead the proletariat in overthrowing capitalism and establishing socialism, ultimately progressing to communism.

The vanguard works to engage the working class in revolutionary politics and to strengthen proletarian political power against the bourgeoisie.

This theory generally serves as a rationale for the leading role of the Communist party, which is often enshrined in the country's constitution if the party attains state power.

Vladimir Lenin popularised political vanguardism as conceptualised by Karl Kautsky, detailing his thoughts in one of his earlier works, What is to be done?. Lenin argued that Marxism's complexity and the hostility of the establishment (the autocratic, semi-feudal state of Imperial Russia) required that a close-knit group of individuals pulled from the working class vanguard to safeguard the revolutionary ideology within the particular circumstances presented by the Tsarist régime (Russian Empire) at the time. While Lenin wished for a revolutionary organisation akin to the contemporary Social Democratic Party of Germany, which was open to the people and more democratic in organisation, the Russian autocracy prevented this.

Leninists argue that Lenin's ideal vanguard party would have open membership: "The members of the Party are they who accept the principles of the Party program and render the Party all possible support." This party could be completely transparent, at least internally: the "entire political arena is as open to the public view as is a theatre stage to the audience". A party that supposedly implemented democracy to such an extent that "the general control (in the literal sense of the term) exercised over every party man in the politics brings into existence an automatically operating mechanism which produces what in biology is called the "survival of the fittest"". The party would be completely open while educating the proletariat to remove the false consciousness that had been instilled in them.

In its first phase, the vanguard party would exist for two reasons. Firstly, it would protect Marxism from outside corruption from other ideas, as well as advance its plans. Secondly, it would educate the proletariat in Marxism in order to cleanse them of their "false individual consciousness" and instill the revolutionary "class consciousness" in them.

Our task is not to champion the degrading of the revolutionary to the level of an amateur, but to raise the amateurs to the level of revolutionaries.

If the party is successful in their goal, on the eve of revolution, a critical mass of the working class population would be prepared to usher forth the transformation of society. Furthermore, a great number of them, namely their most dedicated members, would belong to the party cadres as professional revolutionaries, and would be elected to leadership positions by the mass party membership. Thus the organisation would quickly include the entire working class.