The Mask of Sanity: An Attempt to Clarify Some Issues About the So-Called Psychopathic Personality is a book written by American psychiatrist Hervey M. Cleckley, first published in 1941, describing Cleckley's clinical interviews with patients in a locked institution. It is considered a seminal work and the most influential clinical description of psychopathy in the twentieth century. The basic elements of psychopathy outlined by Cleckley are still relevant today. The title refers to the normal "mask" that conceals the mental disorder of the psychopathic person in Cleckley's conceptualization.