Shirley Ardell Mason (January 25, 1923 – February 26, 1998) was an American psychiatric patient and commercial artist who was reputed to have multiple personality disorder, now called dissociative identity disorder. Her life was fictionalized in 1973 in the book Sybil, and two films of the same name were made in 1976 and 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 was born and raised in Dodge Center, Minnesota, the only child of Walter Mason (a carpenter and architect) and Martha Alice "Mattie" Atkinson. In regard to Mason's mother: "...many people in Dodge Center say Mattie" — "Hattie" in the book — "was bizarre," according to Bettie Borst Christensen, who grew up across the street. "She had a witch-like laugh....She didn't laugh much, but when she did, it was like a screech." Christensen remembers Mason's mother walking around after dark, looking in the neighbors' windows. At one point, Mason's mother was reportedly diagnosed with schizophrenia.
In the early 1950s, Mason was a substitute teacher and a student at Columbia University. She had long suffered from blackouts and emotional breakdowns, and finally entered psychotherapy with Cornelia B. Wilbur, a Freudian psychiatrist. Their sessions together are the basis of the book.
From 1968-1973, she taught art at Rio Grande College, in Rio Grand, Ohio (now the University of Rio Grande).
Some people in Mason's home town, reading the book, recognized Mason as Sybil. By that time, Mason had severed nearly all ties with her past and was living in West Virginia. She later moved to Lexington, Kentucky, where she lived near Dr. Wilbur. She taught art classes at a community college and ran an art gallery out of her home for many years.
Wilbur diagnosed Mason with breast cancer in 1990, and she declined treatment; it later went into remission. The following year Wilbur developed Parkinson's disease and Mason moved into Wilbur's house to take care of her until Wilbur's death in 1992. Mason died of breast cancer on February 26, 1998.