Johann Georg Schrepfer, or Johann Georg Schröpfer (1738? – 8 October 1774 in Leipzig) was a German charlatan, independent Freemason, and necromancer. He performed ghost-raising séances for which he secretly used special effects, possibly including magic lantern projections of ghosts on smoke, which inspired the phantasmagoria shows popular in Europe from the 1790s to the 1830s.
Little is certain about Schrepfer's life. Many accounts stem from either adherent or opposing Freemasons and Schrepfer himself was an impostor who told many lies about himself.
Schrepfer's year of birth is often stated to be 1730 and sometimes as 1739, but he was baptized in Nürnberg on March 26, 1738. He was listed as the eighth child of the host of "Zum Rothen Roße". Father Schrepfer later ran the "Goldenen Lamm" and seems to have gone bankrupt in 1753. Johann Georg reportedly served for some time as a hussar in the Prussian army at the start of the Seven Years' War. However, he also claimed to have been a cavalry commander with the imperial troops and to have received many wounds in battle (although his autopsy report clearly stated that no scars or signs of old injuries were found on his body). He came to Leipzig in 1759 and started as a "Küper" (controller of goods) in Hotel de Saxe. He became a citizen of the city in August 1761 and was registered as a waiter. September 20, 1761 he married Johanna Katharina Herr, the daughter of the quartermaster of the local tailors. She was already highly pregnant and soon gave birth to their first daughter. In 1769 they purchased the "Weisslederische Coffeé-Hauß" with Johanna's money. It was a café with a billiard room in the very center of town (at the corner of Klostergasse and the Barfußgäßchen, the location of restaurant "Zill's Tunnel" since 1841).
Saxony went through some hunger years in 1770-1771. Schrepfer had debts and his family seemed to live in relative poverty, but he reportedly maintained a frivolous lifestyle and often drank wine with his followers. It was thought he got some financial support from a French Masonic lodge or some Prince elsewhere in the country, often leaving Leipzig to visit them. He started his own Masonic lodge, probably to gain some power and to make money. He often promised people large sums of money and to make them happy. Among the many lies he told were claims that he was a Catholic priest and that he was the son of the French Prince von Conti.