Jackson Clark Gillis (August 21, 1916 – August 19, 2010) was an American radio and television scriptwriter whose career spanned more than 40 years and encompassed a wide range of genres.

After completing his military service, Gillis moved to Los Angeles and took a job writing for radio shows, including the dramas The Whistler and Let George Do It. He moved into television scriptwriting and earned his first credit — for an episode of Racket Squad, a series that starred Reed Hadley — in 1952. He wrote for The Adventures of Superman from 1953 to 1957 and also spent several years writing for Perry Mason and Lassie. His scriptwriting was prolific and varied, and over the years, he worked on shows such as Lost in Space, Hawaii Five-O, and Knight Rider. He wrote for the series Columbo, starring Peter Falk, from 1971 to 1992. He also wrote a pair of detective novels, The Killers of Starfish and Chainsaw.