Eugene Joseph McCarthy (March 29, 1916 – December 10, 2005) was an American politician, writer, and academic from Minnesota who served from 1949 to 1959 in the United States House of Representatives and from 1959 to 1971 in the United States Senate. McCarthy sought the Democratic presidential nomination in the 1968 election, challenging incumbent Lyndon B. Johnson on an anti–Vietnam War platform, and ran unsuccessfully for the Democratic nomination for president on four subsequent occasions.

Born in Watkins, Minnesota, McCarthy became an economics professor after earning a graduate degree from the University of Minnesota. He served as a code breaker for the United States Department of War during World War II. McCarthy became a member of the Minnesota Democratic–Farmer–Labor Party (the state affiliate of the Democratic Party) and in 1948 was elected to the House of Representatives, where he served until being elected to the U.S. Senate in 1958. McCarthy was a prominent supporter of Adlai Stevenson II for the Democratic presidential nomination in 1960, and was himself a candidate for the Democratic vice-presidential nomination in 1964. He co-sponsored the Immigration and Nationality Act of 1965, though he later expressed regret about its impact and became a member of the Federation for American Immigration Reform.

As the 1960s progressed, McCarthy emerged as a prominent opponent of Johnson's handling of the Vietnam War. After Robert F. Kennedy declined the request of a group of antiwar Democrats to challenge Johnson in the 1968 Democratic primaries, McCarthy entered the race on an antiwar platform. Though he was initially given little chance of winning, the Tet Offensive galvanized opposition to the war, and McCarthy finished in a strong second place in the New Hampshire primary. After that, Kennedy entered the race, and Johnson announced that he would not seek reelection. McCarthy and Kennedy each won several primary contests.

The race was upended in June 1968 when Kennedy was assassinated. McCarthy won a plurality of the popular vote and delegate count in the primaries, but the rules did not bind delegates to their primary results. After Kennedy's assassination, his delegates became uncommitted, with most ultimately backing Vice President Hubert Humphrey, who had not actively campaigned in the primaries. He had entered the primaries in April 1968 and was the preferred candidate of President Lyndon B. Johnson. This gave Humphrey the majority needed to secure the Democratic nomination at the 1968 Democratic National Convention.

McCarthy did not seek reelection in the 1970 Senate election. He sought the Democratic presidential nomination in 1972 but fared poorly. He ran in more races after that but was never elected to another office. He ran as an Independent in the 1976 presidential election and won 0.9% of the popular vote. He was a plaintiff in the landmark campaign finance case Buckley v. Valeo and supported Ronald Reagan in the 1980 presidential election.

McCarthy was born in Watkins, Minnesota. He was the son of a deeply religious Catholic woman of German ancestry, Anna Baden McCarthy, and a strong-willed man of Irish descent, Michael John McCarthy Jr., a postmaster and cattle buyer.

McCarthy grew up in Watkins with his parents and three siblings. He attended St. Anthony's Catholic School in Watkins, and spent hours reading his aunt's Harvard Classics. He was influenced by the monks at nearby St. John's Abbey and University in Collegeville, Minnesota, and attended school there, at Saint John's Preparatory School, from which he graduated in 1932. He also went to college at Saint John's University, graduating in 1935. McCarthy earned his master's degree from the University of Minnesota in 1939. He taught in public schools in Minnesota and North Dakota from 1935 to 1940, when he became a professor of economics and education at St. John's, working there from 1940 to 1943.

While at St. John's, he coached the hockey team for one season.