Sphere is a science fiction novel written by Michael Crichton and published in 1987. It has since been made into a movie. A mysterious sphere is discovered inside a time-travelling space ship. Written as a psychological thriller, it explores the human subconscious.

In the book, a group of scientists, including psychologist Norman Johnson, mathematician Harry Adams, biologist Beth Halpern, and astrophysicist Ted Fielding, are called by the United States Navy to the middle of the southern Pacific Ocean to explore what appears to be the underwater crash site of an alien spacecraft. To their surprise, they find that the spacecraft is not alien, but an American craft constructed fifty years in the future. The team also discovers a mysterious spherical artefact of unknown origin, which allows those who have entered it to create things by imagining them. But the team is endangered when they are attacked by creatures (giant squids, sea snakes, and jellyfish) created by their imaginations.

The book was turned into a movie in 1998, directed by Barry Levinson, and a cast including Dustin Hoffman (Norman Johnson, renamed Norman Goodman), Samuel L. Jackson (Harry Adams), and Sharon Stone (Dr Beth Halperin).