Henri Petit (alias Henri-Robert or Henry-Robert) (1899–1985) was a French journalist, Collaborationist under the Vichy regime and far-right activist.
Henri Petit wrote several anti-Semitic and anti-masonic books and collaborated with Henry Coston. He presented himself as an "anti-Jew" candidate for the 1936 legislative elections, won by the Popular Front. Petit then broke with Coston, who accused him of having stolen him money. In 1937, he became the secretary general of Louis Darquier de Pellepoix's Comité antijuif de France (Anti-Jew Committee of France) — Darquier de Pellepoix replaced in May 1942 Xavier Vallat as "Commissioner for Jewish Affairs."
Petit's work influenced the writer Louis-Ferdinand Céline, who shifted more and more to the far-right during his literary career. Céline entertained a literary correspondency with Henri Petit.
In 1939, Petit traveled to Nazi Germany to work in the "World Center of Anti-Semitic Propaganda". He then returned to France after the proclamation by Marshal Philippe Pétain of the Vichy regime, and became in 1940 the chief editor of the Collaborationist newspaper Le Pilori, before being replaced by another team. Petit worked directly with the German services of Nazi propaganda and was, because of that, not really appreciated in Collaborationist circles. At the end of World War II, in August 1944, he left for Germany where his two sons worked as volunteers in the German Army.
On 18 November 1947, during the épuration légale period, he was condemned in absentia to 20 years of prison and to "national degradation" (dégradation nationale). He then lived in clandestinity in Belleville, Paris, and in Meudon. Amnestied in 1959, he then published an astrology magazine, before collaborating with the Fédération d'action nationale et européenne (FANE) neo-Nazi group created in 1966 by Mark Fredriksen. Petit was sentenced several times for "incitation to racial hatred."