Emil Frey-Gessner (19 March 1826, Aarau - 24 July 1917 Genf) was a Swiss entomologist.
At first Emil Frey-Gessner studied mechanical engineering and was until 1865 technical director in the Frey-Gessner family cotton mill.Later he studied natural sciences at the Eidgenössische Technische Hochschule Zürich and became a District Teacher in Brugg then in the Canton of Aarau.
From 1872 he was conservator of the entomological collections at the new museum of Geneva University.