This article is about the libertarian political philosophy within the socialist movement. For the branch of anarchism emphasizing social equality, see Social anarchism. For the type of libertarianism stressing both individual freedom and social equality, see Left-libertarianism. For the political philosophy that incorporates liberal principles to socialism, see Liberal socialism. For the variety of liberalism that endorses a regulated market economy and the expansion of civil and political rights, see Social liberalism.
With its roots in the Age of Enlightenment, libertarian socialism was first constituted as a tendency by the anti-authoritarian faction of the International Workingmen's Association (IWA), during their conflict with the Marxist faction. Libertarian socialism quickly spread throughout Europe and the American continent, reaching its height during the early stages of the Russian Revolution of 1917 and particularly during the Spanish Revolution of 1936. Its defeat during these revolutions led to its brief decline, before its principles were resurrected by the New Left and new social movements of the late 20th century.
While its key principles of decentralisation, workers' control and mutual aid are generally shared across the many schools of libertarian socialism, differences have emerged over the questions of revolutionary spontaneity, reformism, and whether to prioritise the abolition of the state or of capitalism.