"Left-Wing" Communism: An Infantile Disorder by Vladimir Lenin is a critique of certain ultra-left tendencies within the international communist movement during the early 20th century. Lenin addresses "left-wing" factions that reject participation in parliamentary politics, trade unions, and alliances with non-communist forces, arguing that these positions are immature and counterproductive.

Lenin emphasizes the importance of tactical flexibility and the need for communists to engage with existing political and social structures to win over the working class. He critiques the ultra-left for dismissing these as "compromises," asserting that successful revolution requires understanding the material conditions and using every available opportunity to advance the proletarian cause.

Through historical examples, including the success of the Bolsheviks in Russia, Lenin demonstrates how engagement with diverse groups and strategic compromises were essential in building the revolutionary movement. He warns that dogmatic approaches can isolate communists from the masses and weaken the revolutionary struggle.

The work is both a defense of Marxist pragmatism and a guide to revolutionary strategy, emphasizing the need for discipline, adaptability, and connection with the broader working-class movement. It remains a key text for understanding Leninist approaches to revolutionary politics.