The Libertarian Party (LP) is a political party in the United States that promotes civil liberties, non-interventionism, laissez-faire capitalism, and limiting the size and scope of government. The party was conceived in August 1971 at meetings in the home of David F. Nolan in Westminster, Colorado, and was officially formed on December 11, 1971, in Colorado Springs. The organizers of the party drew inspiration from the works and ideas of the prominent Austrian school economist Murray Rothbard. The founding of the party was prompted in part due to concerns about the Nixon administration, the Vietnam War, conscription, and the introduction of fiat money.

The party generally promotes a classical liberal platform, in contrast to the Democratic Party's modern liberalism and progressivism and the Republican Party's conservatism. Gary Johnson, the party's presidential nominee in 2012 and 2016, claims that the Libertarian Party is more culturally liberal than Democrats, and more fiscally conservative than Republicans. Its fiscal policy positions include lowering taxes, abolishing the Internal Revenue Service (IRS), decreasing the national debt, allowing people to opt out of Social Security and eliminating the welfare state, in part by utilizing private charities. Its cultural policy positions include ending the prohibition of illegal drugs, advocating criminal justice reform, supporting same-sex marriage, ending capital punishment, and supporting gun ownership rights.

As of May 2024, it is the third-largest political party in the United States by voter registration. In the 2020 election, the Libertarians gained a seat in the Wyoming House of Representatives, giving them their first state legislative win since 2000. As of May 2024, there are 178 Libertarians holding elected office. As of December 2023, there are 741,930 voters registered as Libertarian in the 31 states that report Libertarian registration statistics and Washington, D.C. The first electoral vote for a woman was that for Tonie Nathan of the party for vice president in the 1972 United States presidential election due to a faithless elector supporter who eschewed his expected votes for President Richard Nixon and Vice President Spiro Agnew in favor of the Libertarian ticket. The first and only Libertarian in Congress was Justin Amash, who joined the Libertarian Party in 2020 and left the U.S. House of Representatives in 2021 after choosing not to seek re-election.

In 2022, the paleolibertarian Mises Caucus (LPMC) became the dominant faction on the Libertarian National Committee, leading to internal conflicts and significant policy changes, such as regarding immigration and abortion.