The 1964 United States presidential election was the 45th quadrennial presidential election. It was held on Tuesday, November 3, 1964. Incumbent Democratic United States President Lyndon B. Johnson defeated Barry Goldwater, the Republican nominee, in a landslide. With 61.1% of the popular vote, Johnson won the largest share of the popular vote of any candidate since the largely uncontested 1820 election, in which no candidate of either party has been able to match or surpass.

Johnson took office on November 22, 1963 and emphasized the continuation of his assassinated predecessor, Kennedy. He easily defeated a primary challenge by Governor George Wallace of Alabama, to win the nomination to a full term. At the 1964 Democratic National Convention, Johnson selected Senator Hubert Humphrey of Minnesota as his running mate. In the Republican contest Senator Barry Goldwater of Arizona, a leader of his party's conservative faction, defeated liberal Governor Nelson Rockefeller of New York and Governor William Scranton of Pennsylvania.

Johnson championed his passage of the Civil Rights Act, and advocated a series of anti-poverty programs collectively known as the Great Society. Goldwater espoused a low-tax, small-government philosophy. Although he supported previous attempts civil rights legislation in 1957 and 1960, Goldwater reluctantly opposed the Civil Rights Act of 1964, saying it violated individual liberty and states' rights. Democrats successfully portrayed Goldwater as a dangerous extremist, most famously in the "Daisy" television advertisement. The Republicans were divided between its moderate and conservative factions, with Rockefeller and other moderate party leaders refusing to campaign for Goldwater. Johnson led by wide margins in all polls during the campaign.

Johnson carried 44 states and the District of Columbia, which voted for the first time in this election. Goldwater won his home state and swept the five states of the Deep South, most of which had not voted for a Republican presidential candidate since the end of Reconstruction in 1877. This was the last time that the Democratic Party won the white vote. This was the first-ever and only election before 1992 in which the Democrats carried Vermont, and the first election since 1912 in which the Democrats carried Maine. Conversely, it was also the first-ever election in which the Republicans carried Georgia.

This was the last election in which the Democratic nominee carried Idaho, Utah, Wyoming, North Dakota, South Dakota, Nebraska, Kansas, or Oklahoma, and the only election ever in which the Democrat carried Alaska. As such, this was the most recent presidential election in which the entire Midwestern region voted Democratic. Iowa and Oregon would not vote Democratic again until 1988, California, Colorado, Illinois, Montana, Nevada, New Hampshire, New Jersey, New Mexico, and Vermont would not vote Democratic again until 1992, while Indiana and Virginia would not vote Democratic again until 2008. As of 2022, this marks the last time that a Democratic presidential candidate has won more than 400 electoral votes.

Johnson's landslide victory coincided with the defeat of many conservative Republican congressmen. The subsequent 89th Congress would pass major legislation such as the Social Security Amendments of 1965 and the Voting Rights Act. The 1964 election marked the beginning of a major, long-term re-alignment in American politics, as Goldwater's unsuccessful bid significantly influenced the modern conservative movement. The movement of conservatives to the Republican Party continued, culminating in the 1980 presidential victory of Ronald Reagan.

Lyndon Baines Johnson (; August 27, 1908 – January 22, 1973), often referred to by his initials LBJ, was an American educator and politician who served as the 36th president of the United States from 1963 to 1969. He had previously served as the 37th vice president from 1961 to 1963 under President John F. Kennedy. A Democrat from Texas, Johnson also served as a U.S. representative, U.S. senator and the Senate's majority leader. He holds the distinction of being one of the few presidents who served in all elected offices at the federal level.

Born in a farmhouse in Stonewall, Texas, to a local political family, Johnson worked as a high school teacher and a congressional aide before winning election to the U.S. House of Representatives in 1937. He won election to the United States Senate in 1948 after narrowly winning the Democratic Party's nomination. He was appointed to the position of Senate Majority Whip in 1951. He became the Senate Democratic leader in 1953 and majority leader in 1954. In 1960 Johnson ran for the Democratic nomination for president. During the convention he came into conflict with the Democratic front-runner, fellow senator John F. Kennedy. The two men compromised and the Kennedy-Johnson ticket won in the 1960 presidential election. Vice President Johnson would assume the presidency on November 22, 1963, after President Kennedy was assassinated. The following year Johnson was elected to the presidency when he won in a landslide against Arizona Senator Barry Goldwater. Johnson received 61.1% of the popular vote in the 1964 presidential election; this makes his victory the largest share of the popular vote of any candidate since James Monroe's victory in 1820.

Johnson's domestic policy was aimed to create programs that would expand civil rights, public broadcasting, Medicare, Medicaid, aid to education and the arts, urban and rural development, and public services. Johnson coined the term the "Great Society" in 1964 to describe these efforts. In addition, he sought to create better living conditions for low income Americans by spearheading a campaign unofficially called the "War on Poverty"; assisted by a strong economy, the effort helped millions of Americans rise above the poverty line during his administration. Johnson followed his predecessor's actions in bolstering the space program, and it was under his presidency that NASA's efforts became a top national priority and the Apollo Program was expanded. He enacted the Higher Education Act of 1965 which established federally insured student loans. Johnson signed the Immigration and Nationality Act of 1965 which laid the groundwork for U.S. immigration policy today. Johnson's opinion on the issue of civil rights put him at odds with other white, southern Democrats. His civil rights legacy was shaped by signing the Civil Rights Act of 1964, the Voting Rights Act of 1965, and the Civil Rights Act of 1968. During his presidency the American political landscape transformed significantly, as white southerners who were Democratic stalwarts gradually moved to the Republican Party and black voters began moving towards the Democratic Party. Because of his domestic agenda, Johnson's presidency marked the peak of modern liberalism in the United States.Johnson's presidency took place in Cold War America and thus he prioritized halting the expansion of Marxist-Leninist governments. Prior to 1964, the U.S. already had a noticeable presence in Vietnam by providing weapons, training, and aid to South Vietnam in order to stem the communist movement in the region. In 1964, following a naval skirmish, Congress passed the Gulf of Tonkin Resolution, which granted Johnson the power to launch a full military campaign in Southeast Asia, marking the escalation of American involvement in the Vietnam War. The number of American military personnel in Vietnam increased dramatically, and as the war progressed, American casualties soared along with deaths of Vietnamese civilians. In 1968, the Tet Offensive inflamed the anti-war movement and public opinion dramatically turned against the war. Many called an end to U.S. involvement, and opposition to the war surged among draft-age students on university campuses.

At home, Johnson faced further troubles when summer riots began in major cities in 1965 and crime rates soared. His political opponents seized the opportunity and raised demands for "law and order" policies. Johnson began his presidency with near universal support, however his approval declined throughout the decade as the public became frustrated with both the war and domestic unrest. Johnson initially sought to run for re-election, however following a disappointing result in the New Hampshire primary he withdrew his candidacy. The Vietnam War was a major election issue and the 1968 presidential election saw Republican candidate Richard Nixon defeat Johnson's vice president Hubert Humphrey in a landslide. At the end of his presidency in 1969, Johnson returned to his Texas ranch and kept a low profile until he died of a heart attack in 1973.

Johnson is one of the most controversial presidents in American history; public opinion of his legacy has continuously evolved since his death. Historians and scholars rank Johnson in the upper tier because of his domestic policies; his administration passed many major laws that made serious advancements in civil rights, health care, and welfare. However, he is widely condemned for his role in escalating the Vietnam War and the consequences that came along with it, including the deaths of 58,220 American service members, dropping over 7.5 million tons of explosives over Vietnam, and the use of the noxious herbicide Agent Orange.