Flora Rheta Schreiber (April 24, 1918 – November 3, 1988), an American journalist, was the author of the 1973 bestseller Sybil, the story of a woman (identified years later as Shirley Ardell Mason) who had a dissociative identity disorder and allegedly had 16 different personalities. As Mason had insisted on protection of her privacy, Schreiber gave her the cover identity of Sybil Isabel Dorsett.

Schreiber was an English instructor at John Jay College of Criminal Justice for many years. She later wrote The Shoemaker, a book documenting the true story of Joseph Kallinger, a serial killer who was diagnosed with paranoid schizophrenia.

Schreiber's papers are housed in the Lloyd Sealy Library Special Collections at John Jay College. The collection is comprehensive documentation of her life and career.