The name "Sybil" has become synonymous with multiple personalities ever since the book of that name by Flora Rheta Schreiber, which in turn became a hit movie in 1976 starring Sally Field.
The real-life Sybil, whose experiences were fictionalized in the book and film, was based on the life of Shirley Ardell Mason. Both the book and the films used the name Sybil Isabel Dorsett to protect her identity, but thereafter her real identity came out.
According to Wikipedia, Shirley Mason had at least 16 different personalities:
Sybil Isabel Dorsett: a depleted person; the waking self. Victoria Antoinette Scharleau: nicknamed Vicky; a self-assured, sophisticated, attractive blonde; the memory trace of Sybil's selves. Peggy Lou Baldwin: an assertive, enthusiastic, and often angry pixie with a pug nose, a Dutch haircut, and a mischievous smile. Peggy Ann Baldwin: a counterpart of Peggy Lou with similar physical characteristics; she is more often fearful than angry. Mary Lucinda Saunders Dorsett: a thoughtful, contemplative, maternal, homeloving person; she is plump and has long dark-brown hair parted on the side. Marcia Lynn Dorsett: last name sometimes Baldwin; a writer and painter; extremely emotional; she has a shield-shaped face, gray eyes, and brown hair parted on the side. Vanessa Gail Dorsett: intensely dramatic and extremely attractive; a tall redhead with a willowy figure, light brown eyes, and an expressive oval face. Mike Dorsett: one of Sybil's two male selves; a builder and a carpenter, he has olive skin, dark hair, and brown eyes. Sid Dorsett: one of Sybil's two male selves; a carpenter and a general handyman; he has fair skin, dark hair, and blue eyes. Nancy Lou Ann Baldwin: interested in politics as fulfillment of biblical prophecy and intensely afraid of Roman Catholics; fey; her physical characteristics resemble those of the Peggys. Sybil Ann Dorsett: listless to the point of neurasthenia; pale and timid with ash-blonde hair, an oval face, and a straight nose. Ruthie Dorsett: a baby; one of the lesser developed selves. Clara Dorsett: intensely religious; highly critical of the waking Sybil. Helen Dorsett: intensely afraid but determined to achieve fulfillment; she has light brown hair, hazel eyes, a straight nose, and thin lips. Marjorie Dorsett: serene, vivacious, and quick to laugh; a tease; a small, willowy brunette with fair skin and a pug nose. The Blonde: nameless; a perpetual teenager; has blonde curly hair and a lilting voice.
After the events depicted in the book and film, Mason moved to Lexington, KY. In Lexington she operated an art gallery out of her home taught classes in painting. After Mason died of breast cancer on February 26, 1998, her legacy as an artist continues with the Lexington-based sybil.biz website.