Judith Guest (born March 29, 1936), in Detroit, Michigan) is an American novelist and screenwriter.

The great-niece of Edgar A. Guest (1881-1959), who had been a Poet Laureate of Michigan, Judith Guest graduated from a Detroit High school in 1954 then studied English and psychology at the University of Michigan, graduating with a BA in Education. She taught at a public school for a number of years before making the decision to devote herself full time to completing a novel.

Her first book, Ordinary People, published in 1976, was made into a 1980 film that won the Academy Award for Best Picture. This novel, and her two other works, Second Heaven (1982), and Errands (1997) are about adolescent children forced to deal with a crisis in their family. She also wrote the screenplay for the 1987 film, Rachel River.

In 1988 she published the mystery, Killing Time in St. Cloud. He most recent book was released in 2004 under the title, The Tarnished Eye : A Novel of Suspense and is loosely based on a true unsolved crime in her native Michigan.