William Hornbeck (August 23, 1901 – October 11, 1983) was an American film editor and film industry executive. In a 1977 poll of film editors, he had been called "the best film editor the industry has produced."

He was nominated four times for the Academy Award for Best Film Editing, and won the award for A Place in the Sun (1951). Other important credits include It's a Wonderful Life (1946), Giant (1956), and I Want to Live! (1958). He edited films from notable directors including Zoltan Korda, Frank Capra, and George Stevens. Universal Pictures almost brought him on board to completely re-edit George Lucas' American Graffiti.Hornbeck started his editing career in his teens with the Keystone Studios, which were located close to his family's home in Los Angeles, California. In the 1920s he became head of the editing department, working on dozens of films each year. In 1934 he went to England, where he headed the editing department for Alexander Korda's film production company. He was generally credited as the "supervising editor"; an exception was The Scarlet Pimpernel (1934), where he was credited as the editor. In 1941 he returned to the United States, and during World War II he served in the Pictorial Service of the Signal Corps of the United States Army. His unit, which produced the films in the Why We Fight series, was led by Frank Capra. Following the war he worked as an editor for a succession of studios and as a freelance editor. In 1960 Hornbeck became the Supervisor for Editorial Operations for Universal Pictures. In 1966 he became a vice-president of the same company. Hornbeck retired in 1976.Hornbeck was one of the original members of the American Cinema Editors, the honorary society of film editors, when it was founded in 1950. Hornbeck died in 1983. In her appreciation, Jeanine Basinger wrote "A true pioneer and a major international influence on film editing, Hornbeck and his work should be remembered for its quality and influence, as well as for his contribution in terms of training a whole generation of young editors in both England and America." Some of his papers are included in the Ogden and Mary Louise Reid Cinema Archives at Wesleyan University