Left-libertarianism, also known as left-wing libertarianism, is a political philosophy and type of libertarianism that stresses both individual freedom and social equality. Left-libertarianism represents several related yet distinct approaches to political and social theory. Its classical usage refers to anti-authoritarian varieties of left-wing politics such as anarchism, especially social anarchism, communalism, and libertarian Marxism, collectively termed libertarian socialism. A portion of the left wing of the green movement, including adherents of Murray Bookchin's social ecology, are also generally considered left-libertarian.

In the United States, libertarianism is a political philosophy promoting individual liberty. According to common meanings of conservatism and liberalism in the United States, libertarianism has been described as conservative on economic issues and liberal on personal freedom, often associated with a foreign policy of non-interventionism. Broadly, there are four principal traditions within libertarianism, namely the libertarianism that developed in the mid-20th century out of the revival tradition of classical liberalism in the United States after liberalism associated with the New Deal; the libertarianism developed in the 1950s by anarcho-capitalist author Murray Rothbard, who based it on the anti-New Deal Old Right and 19th-century libertarianism and American individualist anarchists such as Benjamin Tucker and Lysander Spooner while rejecting the labor theory of value in favor of Austrian School economics and the subjective theory of value; the libertarianism developed in the 1970s by Robert Nozick and founded in American and European classical liberal traditions; and the libertarianism associated with the Libertarian Party, which was founded in 1971, including politicians such as David Nolan and Ron Paul.