Shirley Ardell Mason, American psychiatric patient (d. 1998)
Shirley Ardell Mason (January 25, 1923 – February 26, 1998) was an American art teacher who was reputed to have dissociative identity disorder (previously known as multiple personality disorder). Her life was purportedly described, with adaptations to protect her anonymity, in 1973 in the book Sybil, subtitled The True Story of a Woman Possessed by 16 Separate Personalities. Two films of the same name were made, one released in 1976 and the other in 2007. Both the book and the films used the name Sybil Isabel Dorsett to protect Mason's identity, though the 2007 remake stated Mason's name at its conclusion.

Mason's diagnosis and treatment under Cornelia B. Wilbur have been criticized, with allegations that Wilbur manipulated or possibly misdiagnosed Mason.