Robert Jay Lifton is an American psychiatrist and author, chiefly known for his studies of the psychological causes and effects of wars and political violence, and for his theory of thought reform. He was an early proponent of the techniques of psychohistory.

Psychohistory is an amalgam of psychology, history, and related social sciences and the humanities. Its proponents claim to examine the "why" of history, especially the difference between stated intention and actual behavior. It works to combine the insights of psychology, especially psychoanalysis, with the research methodology of the social sciences and humanities to understand the emotional origin of the behavior of individuals, groups and nations, past and present. Work in the field has been done in the areas of childhood, creativity, dreams, family dynamics, overcoming adversity, personality, political and presidential psychobiography. There are major psychohistorical studies of anthropology, art, ethnology, history, politics and political science, and much else.