Gertrud Theiler (11 September 1897 – 2 May 1986) was a South African parasitologist and teacher most noted for her work with nematodes and ticks.

[1] She went to Europe to undertake postgraduate work in helminthology at the University of Neuchâtel, Switzerland, where she took her Doctor of Science degree in 1923.

[1] The subject of her doctoral thesis is The Strongylids and other Nematodes Parasitic in The Intestinal Tract of South African Equines (PhD).

[1] In 1939 she lectured at Rhodes University College, before accepting a research post in the entomology section at Onderstepoort Veterinary Institute, where she studied ticks for the following 25 years, becoming well known around the world in her field.

[6] She was a sister of virologist Max Theiler, who was awarded the 1951 Nobel Prize in Physiology or Medicine for development of the yellow fever vaccine.