The Heritage Foundation (or simply Heritage) is an American right-wing think tank based in Washington, D.C. Founded in 1973, it took a leading role in the conservative movement in the 1980s during the presidency of Ronald Reagan, whose policies were taken from Heritage Foundation studies, including its Mandate for Leadership.

The Heritage Foundation has had significant influence in U.S. public policy making, and has historically been ranked among the most influential public policy organizations in the United States. In 2010, it founded a sister organization, Heritage Action, an influential activist force in conservative and Republican politics.

Heritage leads Project 2025, also known as the 2025 Presidential Transition Project, an extensive plan that includes appointing ideologically aligned civil servants, restricting abortion access, opposing LGBTQ+ rights, transforming federal agencies for political purposes, and imposing strict immigration policies.

The foundation was established on February 16, 1973, during the Nixon administration by Paul Weyrich, Edwin Feulner, and Joseph Coors. Growing out of the new business activist movement inspired by the Powell Memorandum, Weyrich and Feulner sought to create a conservative version of the Brookings Institution that advanced conservative policies.

Coors was Heritage's earliest funding source, seeding the organization with an initial $250,000. Billionaire Richard Mellon Scaife followed up a year later, using the Scaife Family Charitable Trust to donate tens of millions to the foundation over the next two decades as its primary donor. Weyrich was the foundation's first president. Under Weyrich's successor, Frank J. Walton, the Heritage Foundation began using direct mail fundraising, which contributed to the growth of its annual income, which reached $1 million in 1976. By 1981, the annual budget was $5.3 million.

The foundation advocated pro-business policies and anti-communism in its early years, but distinguished itself from the American Enterprise Institute (AEI) by also advocating for cultural issues important to Christian conservatives. But throughout the 1970s, the Heritage Foundation remained small relative to Brookings and AEI.

In January 1981, the Heritage Foundation published Mandate for Leadership, a comprehensive report aimed at reducing the size of the federal government. It provided public policy guidance to the incoming Reagan administration, and included over 2,000 specific policy recommendations for the Reagan administration to use the federal government to advance conservative policies. The report was well received by the White House, and several of its authors went on to take positions in the Reagan administration. Ronald Reagan liked the ideas so much that he gave a copy to each member of his cabinet to review. About 60% of the 2,000 Heritage proposals were implemented or initiated by the end of Reagan's first year in office. Reagan later called the Heritage Foundation a "vital force" during his presidency.

The foundation was influential in developing and advancing the Reagan Doctrine, a key Reagan administration foreign policy initiative under which the U.S. began providing military and other support to anti-communist resistance movements fighting Soviet-aligned governments in Afghanistan, Angola, Cambodia, Nicaragua, and other nations during the final years of the Cold War.