Richard Nixon's tenure as the 37th president of the United States began with his first inauguration on January 20, 1969, and ended when he resigned on August 9, 1974, in the face of almost certain impeachment and removal from office, the only U.S. president ever to do so. He was succeeded by Gerald Ford, whom he had appointed vice president after Spiro Agnew became embroiled in a separate corruption scandal and was forced to resign. Nixon, a prominent member of the Republican Party from California who previously served as vice president for two terms under president Dwight D. Eisenhower from 1953 to 1961, took office following his narrow victory over Democratic incumbent vice president Hubert Humphrey and American Independent Party nominee George Wallace in the 1968 presidential election. Four years later, in the 1972 presidential election, he defeated Democratic nominee George McGovern, to win re-election in a landslide. Although he had built his reputation as a very active Republican campaigner, Nixon downplayed partisanship in his 1972 landslide re-election.

Nixon's primary focus while in office was on foreign affairs. He focused on détente with the People's Republic of China and the Soviet Union, easing Cold War tensions with both countries. As part of this policy, Nixon signed the Anti-Ballistic Missile Treaty and SALT I, two landmark arms control treaties with the Soviet Union. Nixon promulgated the Nixon Doctrine, which called for indirect assistance by the United States rather than direct U.S. commitments as seen in the ongoing Vietnam War. After extensive negotiations with North Vietnam, Nixon withdrew the last U.S. soldiers from South Vietnam in 1973, ending the military draft that same year. To prevent the possibility of further U.S. intervention in Vietnam, Congress passed the War Powers Resolution over Nixon's veto.

In domestic affairs, Nixon advocated a policy of "New Federalism", in which federal powers and responsibilities would be shifted to state governments. However, he faced a Democratic Congress that did not share his goals and, in some cases, enacted legislation over his veto. Nixon's proposed reform of federal welfare programs did not pass Congress, but Congress did adopt one aspect of his proposal in the form of Supplemental Security Income, which provides aid to low-income individuals who are aged or disabled. The Nixon administration adopted a "low profile" on school desegregation, but the administration enforced court desegregation orders and implemented the first affirmative action plan in the United States. Nixon also presided over the creation of the Environmental Protection Agency and the passage of major environmental laws like the Clean Water Act, although that law was vetoed by Nixon and passed by override. Economically, the Nixon years saw the start of a period of "stagflation" that would continue into the 1970s.

Nixon was far ahead in the polls in the 1972 presidential election, but during the campaign, Nixon operatives conducted several illegal operations designed to undermine the opposition. They were exposed when the break-in of the Democratic National Committee Headquarters ended in the arrest of five burglars. This kicked off the Watergate Scandal and gave rise to a congressional investigation. Nixon denied any involvement in the break-in. However, after a tape emerged revealing that Nixon had known about the White House connection to the burglaries shortly after they occurred, the House of Representatives initiated impeachment proceedings. Facing removal by Congress, Nixon resigned from office.

Though some scholars believe that Nixon "has been excessively maligned for his faults and inadequately recognised for his virtues", Nixon is generally ranked as a below average president in surveys of historians and political scientists.

Richard Nixon had served as vice president from 1953 to 1961, and had been defeated in the 1960 presidential election by John F. Kennedy. In 1962, Nixon ran for governor of California against incumbent Pat Brown, and was defeated handily, leading the media to label him as a "loser". This defeat was widely believed to be the end of his career; in an impromptu concession speech the morning after the election, Nixon famously blamed the media for favoring his opponent, saying, "you won't have Nixon to kick around anymore because, gentlemen, this is my last press conference."

In the years after his defeat, Nixon established himself as an important party leader who appealed to both moderates and conservatives. Nixon entered the race for the 1968 Republican presidential nomination confident that, with the Democrats torn apart over the war in Vietnam, a Republican had a good chance of winning the presidency in November, although he expected the election to be as close as in 1960. One year prior to the 1968 Republican National Convention the early favorite for the party's presidential nomination was Michigan governor George Romney, but Romney's campaign foundered on the issue of the Vietnam War. Nixon established himself as the clear front-runner after a series of early primary victories. His chief rivals for the nomination were Governor Ronald Reagan of California, who commanded the loyalty of many conservatives, and Governor Nelson Rockefeller of New York, who had a strong following among party moderates.

At the August Republican National Convention in Miami Beach, Florida, Reagan and Rockefeller discussed joining forces in a stop-Nixon movement, but the coalition never materialized and Nixon secured the nomination on the first ballot. He selected Governor Spiro Agnew of Maryland as his running mate, a choice which Nixon believed would unite the party by appealing to both Northern moderates and Southerners disaffected with the Democrats. The choice of Agnew was poorly received by many; a Washington Post editorial described Agnew as "the most eccentric political appointment since the Roman Emperor Caligula named his horse a consul. In his acceptance speech, Nixon articulated a message of hope, stating, "We extend the hand of friendship to all people... And we work toward the goal of an open world, open sky, open cities, open hearts, open minds."