Richard Kaczynski is an American writer and lecturer in the fields of social psychology, metaphysical beliefs and new religious movements. He is known for his biography of the occultist Aleister Crowley, Perdurabo: The Life of Aleister Crowley, described by The Times Literary Supplement as "the major biography to date", and by Didrik Søderlind in the Norwegian daily Aftenposten as the best biography of Crowley.