Lyndon Hermyle LaRouche, Jr. (pronounced /ləˈruːʃ/; born September 8, 1922) is an American self-styled economist, political activist, and the founder of several political organizations known collectively as the LaRouche movement. He has been a perennial candidate for President of the United States, having run in eight elections since 1976, once as a U.S. Labor Party candidate and seven times as a candidate for the Democratic Party nomination. He is the founder and contributing editor of the Executive Intelligence Review, and has written prolifically on economic, scientific, and political topics, as well as on history, philosophy, and psychoanalysis.

He was sentenced to 15 years' imprisonment in 1988 for conspiracy to commit mail fraud and tax code violations, but continued his political activities from behind bars until his release in 1994 on parole. His defenders believe the prosecution was a politically motivated conspiracy involving government officials and a mass-media brainwashing campaign. His appellate attorney, Ramsey Clark, a former U.S. Attorney General, argued that the case represented an unprecedented abuse of power by the U.S. government in an effort to destroy the LaRouche movement.

LaRouche provokes sharply contrasting views. His supporters see him as a political leader in the tradition of Roosevelt and Martin Luther King, Jr., and a brilliant thinker who has been unfairly persecuted, while critics regard him as a cult leader, a conspiracy theorist, a fascist, and an anti-Semite. Norman Bailey, formerly with the National Security Council, described LaRouche's staff in 1984 as one of the best private intelligence services in the world, while the Heritage Foundation has said that he leads "what may well be one of the strangest political groups in American history."