The United States Institute of Peace (USIP) is an American independent, nonprofit, national institute founded and funded by the U.S. Congress and tasked with promoting conflict resolution and prevention worldwide. It provides research, analysis, and training to individuals in diplomacy, mediation, and other peace-building measures.

Following years of proposals for a national peace academy, USIP was established in 1984 by congressional legislation signed into law by President Ronald Reagan. It is officially nonpartisan and independent, receiving funding only through a congressional appropriation to prevent outside influence. The institute is governed by a bipartisan board of directors with 15 members, which must include the secretary of defense, the secretary of state, and the president of the National Defense University. The remaining 12 members are appointed by the president and confirmed by the Senate.

The institute's headquarters is in the Foggy Bottom neighborhood of Washington, D.C., at the northwest corner of the National Mall near the Lincoln Memorial and Vietnam Veterans Memorial. It employed around 300 personnel and trained more than 65,000 professionals since its inception.

In February 2025, President Donald Trump signed an executive order with an intention to dismantle the USIP. In March, Trump ordered most of USIP's board of directors to be fired. Under statute, the president may remove board members with the approval of the majority of the board or several congressional committees. The Department of Government Efficiency subsequently entered the USIP building to replace its leadership, fire its staff, and assume building ownership. Some of USIP's former leadership contested the legality of these moves in court, citing the agency's independent structure, and on May 19, Judge Beryl Howell ruled in favor of USIP. On June 27, Howell’s ruling was lifted in federal appeals court.

The United States Institute of Peace Act, passed in 1984 and codified at 22 U.S.C. ch. 56, calls for the institute to "serve the people and the government through the widest possible range of education and training, basic and applied research opportunities, and peace information services on the means to promote international peace and the resolution of conflicts among the nations and peoples of the world without recourse to violence."

The institute carries out this mission by operating programs in conflict zones, conducting research and analysis, operating a training academy and public education center, providing grants for research and fieldwork, convening conferences and workshops, and building the academic and policy fields of international conflict management and peacebuilding. On many of its projects, the institute works in partnership with non-governmental organizations, higher and secondary educational institutions, international organizations, local organizations, and U.S. government agencies, including the State Department and the Department of Defense.

The United States Institute of Peace was created in 1984 when President Ronald Reagan signed the Department of Defense Authorization Act, 1985. As part of his signing statement, Reagan wrote: "I have been advised by the Attorney General that section 1706(f), relating to the President's power to remove members of the Board of Directors of the Institute, is neither intended to, nor has the effect of, restricting the President's constitutional power to remove those officers."

Senator Jennings Randolph joined senators Mark Hatfield and Spark Matsunaga and Representative Dan Glickman in an effort to form a national peace academy akin to the national military academies. The 1984 act creating USIP followed from a 1981 recommendation of a commission formed to examine the peace academy issue appointed by President Jimmy Carter and chaired by Matsunaga.