Johann Joseph Gassner (22 August 1727 in Braz, near Bludenz, Vorarlberg – 1779 Pondorf, now part of Winklarn, Bavaria) was a noted exorcist.

While a Catholic priest at Klösterle he gained a wide celebrity by professing to "cast out devils" and to work cures on the sick by means simply of prayer; he was attacked as an impostor, but the bishop of Regensburg, who believed in his honesty, bestowed upon him the cure of Pondorf.

Gassner's methods have been linked to a special form of hypnotic training by Burkhard Peter, who has described them as a predecessor of modern hypnosis.^[1] Henri Ellenberger, in his "Discovery of the Unconscious", placed the dispute between Gassner and Franz Anton Mesmer at the center of modern psychotherapy.^[2]

• Royal Commission on Animal Magnetism

• Midelfort, H. C. Erik. Exorcism and Enlightenment: Johann Joseph Gassner and the demons of eighteenth-century Germany (New Haven: Yale University Press, 2005). ISBN 0-300-10669-6.
• Gassner at the Catholic Encyclopedia

This article incorporates text from a publication now in the public domain: Wood, James, ed. (1907). The Nuttall Encyclopædia. London and New York: Frederick Warne. {{cite encyclopedia}}: Missing or empty |title= (help)