Gustav L. Mayr (12 October 1830 in Vienna – 14 July 1908 in Vienna) was an Austrian entomologist and professor in Budapest and Vienna. He specialised in Hymenoptera, being particularly known for his studies of Formicidae.
In 1868, he was the first to describe the Argentine ant. He is credited with naming the harvesting ant species, Aphaenogaster treatae, for naturalist Mary Davis Treat in honor of her research on the species.
- Formicidae [der Novara-Expedition]. Vienna 1865.
- Die Ameisen des baltischen Bernsteins. Königsberg: Koch, 1868.
- Feigeninsecten. Vienna: Hölder, 1885.
- Hymenopterologische Miscellen. Vienna: Hölder, 1902.
- Formiciden aus Ägypten und dem Sudan. (1903).