Antipope Gregory XVII may refer to:
Clemente Domínguez y Gómez (1946–2005), self-proclaimed pope, leader of the Palmarian Catholic Church Jean-Gaston Tremblay (1928–2011), self-proclaimed pope, leader of the Apostles of Infinite Love
See also Giuseppe Siri conspiracy theory, the claim that Cardinal Giuseppe Siri was elected pope in 1958, with the name Gregory XVII Earthly Powers, a novel by Anthony Burgess that includes a character named Pope Gregory XVII