The Libertarian Party (LP) is a right-libertarian political party in the United States. The world's first explicitly libertarian party, it was conceived in August 1971 at meetings in the home of David 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's wage and price controls, the Vietnam War, conscription, and the introduction of fiat money. In 2022, the paleoconservative Mises Caucus (LPMC) staged a successful takeover and became the dominant faction on the Libertarian National Committee, shifting the party in a right-wing direction. The change resulted in internal conflicts and significant policy changes. As a result, several state-affiliated chapters distanced or disavowed themselves of the National Committee and formed their own independent state-level parties. Other defectors formed the Classical Liberal Caucus and Liberal Party USA.

The party generally supports "personal liberty" and fiscal conservatism, non-interventionism, laissez-faire capitalism and limiting the size and scope of government. Gary Johnson, the party's presidential nominee in 2012 and 2016, claims that the Libertarian Party is more socially liberal than Democrats, and more fiscally conservative than Republicans. Its fiscal policy positions include lowering taxes and abolishing the Internal Revenue Service (IRS), decreasing the national debt, and phasing out Social Security and the welfare state in part by utilizing private charities. It supports ending the public school system and disbanding Medicare and Medicaid to return to a free-market healthcare system. Its social policy positions include ending the prohibition of illegal drugs, advocating criminal justice reform through the legalization of all victimless crimes, supporting same-sex marriage, ending capital punishment, and supporting the right to keep and bear arms.

As of November 2024, it is the third-largest political party in the United States by voter registration.