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- Hermann von Ihering (1850–1930), German naturalist
- Johann Karl Wilhelm Illiger (1775–1813), German entomologist
- Jan Ingenhousz (1730–1799), Dutch-born British botanist
- Tom Iredale (1880–1972), English conchologist and ornithologist
- Paul Erdmann Isert (1756–1789), German botanist
Read more about this topic: List Of Biologists