Lumpenproletariat (/ˌlʌmpənprlɪˈtɛəriət/) refers – primarily in Marxist theory – to the underclass devoid of class consciousness.[1] Karl Marx and Friedrich Engels coined the word in the 1840s and used it to refer to the unthinking lower strata of society exploited by reactionary and counter-revolutionary forces, particularly in the context of the revolutions of 1848. They dismissed the revolutionary potential of the Lumpenproletariat and contrasted it with the proletariat.

The Social Democratic Party of Germany made wide use of the term by the turn of the century. Vladimir Lenin (1870–1924) and Leon Trotsky (1879–1940) followed Marx's arguments and dismissed the revolutionary potential of the group, while Mao Zedong (1893–1976) argued that proper leadership could utilize it. The word Lumpenproletariat, popularized in the West by Frantz Fanon's The Wretched of the Earth in the 1960s, has been adopted as a sociological term. However, what some consider to be its vagueness and its history as a term of abuse has led to some criticism. Some radical groups, most notably the Black Panther Party and the Young Lords, have sought to mobilize the Lumpenproletariat.