The Myth of Mental Illness: Foundations of a Theory of Personal Conduct is a 1961 book by the psychiatrist Thomas Szasz, in which the author criticizes psychiatry and argues against the concept of mental illness. It received much publicity, and has become a classic, well known as an argument that "mentally ill" is a label which psychiatrists have used against people "disabled by living" rather than truly having a disease.

Thomas Stephen Szasz was a Hungarian-American academic and psychiatrist. He served for most of his career as professor of psychiatry at the State University of New York Upstate Medical University in Syracuse, New York. A distinguished lifetime fellow of the American Psychiatric Association and a life member of the American Psychoanalytic Association, he was best known as a social critic of the moral and scientific foundations of psychiatry, as what he saw as the social control aims of medicine in modern society, as well as scientism.