Gustave Le Bon (May 7, 1841 – December 13, 1931) was a French social psychologist, sociologist, and amateur physicist. He was the author of several works in which he expounded theories of national traits, racial superiority, herd behaviour and crowd psychology.
His work on crowd psychology became important in the first half of the twentieth century when it was utilized by media researchers such as Hadly Cantril and Blumer to describe the reactions of subordinate groups to media.
He also contributed to on-going debates in physics about the nature of matter and energy. His book The Evolution of Matter was very popular in France (going through twelve editions), and though some of its ideas — notably that all matter was inherently unstable and was constantly and slowly transforming into luminiferous ether — were taken up favorably by physicists of the day (including Henri Poincaré) though his specific formulations were not given much consideration. In 1896 he reported observing a new kind of radiation, which he termed "black light" (not the same thing as a black light today), though it was later discovered to not exist.
Le Bon was born in Nogent-le-Rotrou, France, and died in Marnes-la-Coquette. He studied medicine and toured Europe, Asia and North Africa in the 1860s to 1880s while writing on archaeology and anthropology, making some money from the design of scientific apparatus. His first great success however was the publication of Les Lois psychologiques de l'évolution des peuples (1894; The Psychology of Peoples), the first work in which he hit upon a popularising style that was to make his reputation secure. His best selling work, La psychologie des foules (1895; English translation The Crowd: A Study of the Popular Mind, 1896), followed soon after.
Le Bon enjoyed considerable security at the centre of French intellectual life thereafter. In 1902, he launched a series of weekly luncheons (les déjeuners du mercredi) to which prominent figures from all the professions were invited to discuss topical issues. The strength of Le Bon's personal networks is apparent form the guest list: in subsequent years, participants included Henri and Raymond Poincaré (cousins, physicist and President of France respectively), Paul Valéry and Henri Bergson.
The ideas put forward in La psychologie des foules played an important role in the early years of group psychology: Sigmund Freud's Massenpsychologie und Ich-Analyse (1921; English translation Group Psychology and the Analysis of the Ego, 1922) was explicitly based on a critique of Le Bon's work.
Le Bon was one of the great popularisers of theories of the unconscious at a critical moment in the formation of new theories of social action. It is arguable that the fascist theories of leadership that emerged in the 1920s owed much to his theories of crowd psychology. Indeed, Hitler's Mein Kampf largely drew on the propaganda techniques proposed in Le Bon's 1895 book.