Joseph Raymond McCarthy (November 14, 1908 – May 2, 1957) was an American politician who served as a Republican U.S. Senator from the state of Wisconsin from 1947 until his death in 1957. Beginning in 1950, McCarthy became the most visible public face of a period in which Cold War tensions fueled fears of widespread Communist subversion. He was noted for making claims that there were large numbers of Communists and Soviet spies and sympathizers inside the United States federal government and elsewhere. Ultimately, McCarthy's tactics and his inability to substantiate his claims led him to be censured by the United States Senate. The term McCarthyism, coined in 1950 in reference to McCarthy's practices, was soon applied to similar anti-communist pursuits. Today the term is used more generally to describe demagogic, reckless, and unsubstantiated accusations, as well as public attacks on the character or patriotism of political opponents.

Born and raised on a Wisconsin farm, McCarthy earned a law degree at Marquette University in 1935 and was elected as a circuit judge in 1939, the youngest in state history. At age 33, McCarthy volunteered for the United States Marine Corps and served during World War II. He successfully ran for the United States Senate in 1946, defeating Robert M. La Follette, Jr. After several largely undistinguished years in the Senate, McCarthy rose suddenly to national fame in February 1950 when he asserted in a speech that he had a list of "members of the Communist Party and members of a spy ring" who were employed in the State Department. McCarthy was never able to prove his sensational charge.

In succeeding years, McCarthy made additional accusations of Communist infiltration into the State Department, the administration of President Truman, Voice of America, and the United States Army. He also used charges of communism, communist sympathies, or disloyalty to attack a number of politicians and other individuals inside and outside of government. With the highly publicized Army–McCarthy hearings of 1954, McCarthy's support and popularity began to fade. On December 2, 1954, the Senate voted to censure Senator McCarthy by a vote of 67 to 22, making him one of the few senators ever to be disciplined in this fashion. McCarthy died in Bethesda Naval Hospital on May 2, 1957, at the age of 48. The official cause of death was acute hepatitis; it is widely accepted that this was exacerbated by alcoholism.