Georg Johann Pfeffer (1854–1931) was a German zoologist, primarily a malacologist, a scientist who studies mollusks.
Pfeffer was born in Berlin. In 1887 he became curator of the Natural History Museum of Hamburg (Naturhistorisches Museum zu Hamburg), which was established in 1843 and destroyed during World War II. Pfeffer's published writings were mainly about cephalopods.
The World Register of Marine Species database lists 133 marine taxa named by Pfeffer
When Pfeffer's name is listed as an authority for a taxon such as the land snail genus Lamellaxis Strebel & Pfeffer, 1882, his name is not simply an orthographic error for the more commonly encountered molluscan authority Pfeiffer, i.e. Ludwig Karl Georg Pfeiffer, who lived 50 years earlier, from 1805 to 1877.
Georg Johann Pfeffer also studied amphibians and reptiles, naming several new species.
Two species of reptiles are named in his honor, Calamaria pfefferi and Trioceros pfefferi.