Barry Morris Goldwater (January 1, 1909 – May 29, 1998) was a five-term United States Senator from Arizona (1953–1965, 1969–1987) and the Republican Party's nominee for President in the 1964 election. He was also a Major General in the U.S. Air Force Reserve. He was known as "Mr. Conservative".

Goldwater is the politician most often credited for sparking the resurgence of the American conservative political movement in the 1960s. He also had a substantial impact on the libertarian movement.

Goldwater rejected the legacy of the New Deal and fought inside the conservative coalition to defeat the New Deal coalition. He lost the 1964 presidential election by a large margin to incumbent Democrat Lyndon B. Johnson. The Johnson campaign and other critics painted him as a reactionary, while supporters praised his crusades against the federal government, labor unions, and the welfare state. His defeat allowed Lyndon Johnson and the Democrats in Congress to pass the Great Society programs, but the defeat of so many older Republicans in 1964 also cleared the way for a younger generation of American conservatives to mobilize. Goldwater was much less active as a national leader of conservatives after 1964; his supporters mostly rallied behind Ronald Reagan, who became governor of California in 1967 and President of the United States in 1981.