Charles-Marie-Gustave Le Bon (7 May 1841 – 13 December 1931) was a leading French polymath whose interests spanned anthropology, psychology, sociology, medicine, invention, and physics. He is most renowned for his 1895 work The Crowd: A Study of the Popular Mind, a foundational text on crowd psychology.

Born in Nogent-le-Rotrou, Le Bon earned his medical degree from the University of Paris in 1866. He chose not to practice medicine formally, instead embarking on a writing career. He authored numerous medical articles and books before joining the French Army during the Franco-Prussian War. The aftermath of the war and his experiences during the Paris Commune of 1871 profoundly influenced his worldview.

Le Bon traveled extensively across Europe, Asia, and North Africa, studying diverse peoples and civilizations through the emerging field of anthropology. During his travels, he invented a portable cephalometer. In the 1890s, he shifted focus to psychology and sociology, producing his most impactful works. Le Bon argued that crowds form a distinct psychological entity with characteristics shaped by their "racial unconscious." Concurrently, he conducted physics experiments and published books on the subject, anticipating concepts like mass–energy equivalence and predicting the Atomic Age.

Despite being marginalized by certain French academic circles for his conservative and reactionary views, Le Bon remained critical of majoritarianism and socialism throughout his life.