Simon Henry Gage (May 20, 1851 – October 20, 1944) was a professor of anatomy, Histology, and Embryology at Cornell University and an important figure in the history of American microscopy.

Simon Henry Gage attended Charlottesville Seminary and the State Normal School at Albany.

As an undergraduate, Gage worked in the Department of Anatomy with Burt Green Wilder teaching in the newly introduced biology courses.

In addition to his work on microscopy and optic projection, Gage did research on the newt, toad, lamprey, on fat digestion and on the pancreas.

Gage, along with Luzerne Corville and the architect, William H. Miller, designed Stimson Hall, which housed the Cornell Medical College.

Gage served as the responsible librarian of the Van Cleef Memorial Library of medicine in Stimson Hall from 1922 to 1944.