O libertarianismo nos Estados Unidos é uma filosofia política e econômica que promove a liberdade individual.Becker, Lawrence C.; Becker, Charlotte B. (2001). Encyclopedia of Ethics: P-W. 3. Taylor & Francis. p. 1562.Paul, Ellen F. (2007). Liberalism: Old and New. Cambridge: Cambridge University Press. p. 187.Christiano, Thomas; John P. Christman (2009). Contemporary Debates in Political Philosophy. "Individualism and Libertarian Rights". Malden, Massachusetts: Wiley-Blackwell. p. 121.Bevir, Mark (2010). Encyclopedia of Political Theory. Thousand Oaks, California: SAGE Publications; Cato Institute. p. 811. O libertarianismo americano tem sido descrito como conservador em questões econômicas e liberal nas esferas pessoal e cultural,Boaz, David; Kirby, David (October 18, 2006). The Libertarian Vote. Cato Institute. frequentemente associado a uma política externa de não-intervencionismo.
De forma geral, a corrente libertarista americana é dividida em duas vertentes principais. De um lado, há a linha desenvolvida pelo autor anarcocapitalista Murray Rothbard, baseada no libertarianismo do século 19 e anarquismo individualista americano, com destaque para as vertentes de Benjamin Tucker e Lysander Spooner. Essa vertente rejeita a teoria do valor-trabalho em favor da escola austríaca e da teoria subjetiva do valor. Do outro, há o libertarianismo que se desenvolveu como um renascimento do liberalismo clássico nos Estados Unidos depois da associação ao New Deal,Tucker, Jeffrey (September 15, 2016). "Where Does the Term "Libertarian" Come From Anyway?" Foundation for Economic Freedom. Retrieved April 7, 2020. que tem como adeptos políticos como David NolanMartin, Douglas (November 22, 2010). "David Nolan, 66, Is Dead; Started Libertarian Party". New York Times. Retrieved November 17, 2019. e Ron Paul.
Embora libertário continue sendo amplamente utilizado para se referir a socialistas antiestatais internacionalmente,Bookchin, Murray (January 1986). "The Greening of Politics: Toward a New Kind of Political Practice". Green Perspectives: Newsletter of the Green Program Project (1). "We have permitted cynical political reactionaries and the spokesmen of large corporations to pre-empt these basic libertarian American ideals. We have permitted them not only to become the specious voice of these ideals such that individualism has been used to justify egotism; the pursuit of happiness to justify greed, and even our emphasis on local and regional autonomy has been used to justify parochialism, insularism, and exclusivity – often against ethnic minorities and so-called deviant individuals. We have even permitted these reactionaries to stake out a claim to the word libertarian, a word, in fact, that was literally devised in the 1890s in France by Elisée Reclus as a substitute for the word anarchist, which the government had rendered an illegal expression for identifying one's views. The propertarians, in effect – acolytes of Ayn Rand, the earth mother of greed, egotism, and the virtues of property – have appropriated expressions and traditions that should have been expressed by radicals but were willfully neglected because of the lure of European and Asian traditions of socialism, socialisms that are now entering into decline in the very countries in which they originated".Fernandez, Frank (2001). Cuban Anarchism. The History of a Movement. Sharp Press. p. 9. "Thus, in the United States, the once exceedingly useful term "libertarian" has been hijacked by egotists who are in fact enemies of liberty in the full sense of the word.""The Week Online Interviews Chomsky". Z Magazine. February 23, 2002. "The term libertarian as used in the US means something quite different from what it meant historically and still means in the rest of the world. Historically, the libertarian movement has been the anti-statist wing of the socialist movement. In the US, which is a society much more dominated by business, the term has a different meaning. It means eliminating or reducing state controls, mainly controls over private tyrannies. Libertarians in the US don't say let's get rid of corporations. It is a sort of ultra-rightism."Ward, Colin (2004). Anarchism: A Very Short Introduction. Oxford University Press. p. 62. "For a century, anarchists have used the word 'libertarian' as a synonym for 'anarchist', both as a noun and an adjective. The celebrated anarchist journal Le Libertaire was founded in 1896. However, much more recently the word has been appropriated by various American free-market philosophers." seu significado nos Estados Unidos se desvia de suas origens políticas em direção ao sentido oposto do espectro político.Goodway, David (2006). Anarchist Seeds Beneath the Snow: Left-Libertarian Thought and British Writers from William Morris to Colin Ward. Liverpool: Liverpool University Press. p. 4. "'Libertarian' and 'libertarianism' are frequently employed by anarchists as synonyms for 'anarchist' and 'anarchism', largely as an attempt to distance themselves from the negative connotations of 'anarchy' and its derivatives. The situation has been vastly complicated in recent decades with the rise of anarcho-capitalism, 'minimal statism' and an extreme right-wing laissez-faire philosophy advocated by such theorists as Rothbard and Nozick and their adoption of the words 'libertarian' and 'libertarianism'. It has therefore now become necessary to distinguish between their right libertarianism and the left libertarianism of the anarchist tradition".Marshall, Peter (2009). Demanding the Impossible: A History of Anarchism. p. 641. "The word 'libertarian' has long been associated with anarchism, and has been used repeatedly throughout this work. The term originally denoted a person who upheld the doctrine of the freedom of the will; in this sense, Godwin was not a 'libertarian', but a 'necessitarian'. It came however to be applied to anyone who approved of liberty in general. In anarchist circles, it was first used by Joseph Déjacque as the title of his anarchist journal Le Libertaire, Journal du Mouvement Social published in New York in 1858. At the end of the last century, the anarchist Sébastien Faure took up the word, to stress the difference between anarchists and authoritarian socialists".The Anarchist FAQ Editorial Collective (11 December 2008). "150 years of Libertarian". Anarchist Writers. The Anarchist Library. Retrieved 31 January 2020.The Anarchist FAQ Editorial Collective (17 May 2017). "160 years of Libertarian". Anarchist Writers. Anarchist FAQ. Retrieved 31 January 2020. O Partido Libertário afirma que "os libertários apoiam a liberdade máxima em questões pessoais e econômicas. Eles defendem um governo muito menor; um que se limita a proteger os indivíduos da coerção e da violência. Os libertários tendem a abraçar a responsabilidade individual, opor-se à burocracia e aos impostos do governo, promover a caridade privada, tolerar estilos de vida diversos, apoiar o livre mercado e defender as liberdades civis".