Jean-Marie Gantois (21 July 1904 – 28 May 1968) was a French Catholic priest (abbé) and a pioneer of Flemish nationalism in French Flanders.
Gantois was born in 1904 in Watten, Nord department, to Flemish parents. He was raised in the French language and learned Dutch at the Catholic seminary of Annappes where he began his studies in 1922. He was influenced by the Flemish circle of the seminary, which promoted the knowledge of Flemish culture, history and language for pastoral purposes. Gantois adopted the Flemish cause as his own and founded the short-lived paper De Vlaemsche Stemme van Vrankryk ("The Flemish Voice in France") in 1923 and the cultural association Vlaamsch Verbond van Frankrijk (VVF, "Flemish Association of France") in 1924.
In the 1920s and 1930s, Gantois wrote extensively for VVF journals and other publications using a number of pseudonyms. He also established personal contacts with numerous other regional leaders of France. At first, Gantois supported French Flanders remaining a part of the French state, insofar as France recognized and respected his region. However, the VVF gradually became more separatist in its politics, and over time abandoned French regionalism as its ideology and increasingly associated with the Greater Netherlands movement, which considered the French Flemish as a part of a single Dutch race, the Dietse volk.
Early during the war, French military authorities banned the VVF. During the German occupation, Gantois revived the activities of the VVF, though he limited them to the cultural field. As a conservative Catholic organization, the VVF had little in common with the Nazi ideology. The organization was not overtly separatist, and French police reports as a late as 1943 concluded that it did not pose a threat to the integrity of the French state. However, because of his vocal Flemish nationalism and perceived extremism, Gantois was relieved of his sacramental duties by Cardinal Achille Liénart.