Gregory Deyermenjian (born 1949, Boston) is a psychologist and explorer. In 1981 he visited the ruins of Vilcabamba la Vieja at Espíritu Pampa, and then turned his attention to the northeast and north of Cusco, Peru. Since the mid-1980s he has made numerous expeditions to Peru investigating Paititi, a legendary lost city that is part of the history and legend of the western Amazon basin. He is a long-term Fellow of The Explorers Club.