Lejaren Arthur Hiller (February 23, 1924, New York City – January 26, 1994, Buffalo, New York) was an American composer. In 1957 he collaborated on the first significant computer music composition, Illiac Suite, with Leonard Issacson. It was his fourth string quartet. In 1958 he founded the Experimental Music Studio at the University of Illinois at Urbana-Champaign. His notable pupils included composers James Fulkerson, Larry Lake, Ilza Nogueira, David Rosenboom, Bernadette Speach and James Tenney.
He was originally trained as a chemist, and worked as a research chemist for DuPont in Waynesboro, Virginia from 1947 to 1952. He developed the first reliable process for dyeing Orlon and coauthored a popular textbook. 
He played piano, oboe, clarinet, and saxophone as a child. He also studied composition with Roger Sessions and Milton Babbitt while earning his chemistry degree at Princeton University. His father, Lejaren Hiller, Sr., was a well-known art photographer who specialized in historical tableaux.
He wrote an article on the Illiac Suite for Scientific American which garnered a lot of attention from the press, generating a storm of controversy. The musical establishment was so hostile to this interloper scientist that both Baker's Biographical Dictionary of Musicians and the New Grove Dictionary of Music and Musicians refused to include him until shortly before his death.
A majority of Hiller's works after 1957 do not involve computers at all, but might include stochastic music, indeterminacy, serialism, Brahmsian traditionalism, jazz, performance art, folksong and counterpoint mixed together. He also collaborated with John Cage for HPSCHD. In 1968, he joined the faculty at University at Buffalo as Slee Professor of Composition, where he established the school's first computer music facility and codirected with Lukas Foss the celebrated Center of the Creative and Performing Arts. His illness forced him to retire in 1989. He died from Alzheimer's disease in 1994.
- James Bohn. "Lejaren Hiller", ems.music.uiuc.edu.
- Lejaren Hiller (1924-1994) © 1994 by Peter Gena.
- Lejaren A. Hiller: Computer Music Pioneer exhibition at Buffalo University (2004)
- A biography about Lejaren A. Hiller