Gustav Tschermak von Seysenegg (19 April 1836 – 24 May 1927) was an Austrian mineralogist.

He was born in Litovel, Moravia, and studied at the University of Vienna, where he obtained a teaching degree.

He studied mineralogy at Heidelberg and Tübingen and obtained a PhD.

In 1871 he established the Mineralogische Mitteilungen (Mineralogical Reports), published after 1878 as the Mineralogische und petrographische Mitteilungen (Mineralogical and Petrographical Reports).

His publications include: He had two sons, Armin von Tschermak-Seysenegg, professor of physiology, and Erich von Tschermak-Seysenegg, a botanist, who were one of the re-discoverers of Mendel's laws of genetics.