Encyclopedias, Almanacs, Transcripts, and Maps
- Gymnolaemata (Marine Bryozoans)
- Gymnophiona (Caecilians)
- Gymnotiformes (South American Knifefishes and Electric Eels)
- Gymnures and Hedgehogs (Erinaceidae)
- Gynocentrism
- Gyōgi
- H'ai Gaon
- Haagen-Smit, Arie Jan (1900 – 1977) Dutch Atmospheric Chemist
- Haavio, Martti
- Habitat Conservation Plans
- Habitat Fragmentation
- Habitat Loss and Species Extinction
- Ḥadīth
- Hadlee, Sir Richard John
- Hadrian, Publius Aelius
- Haeckel, Ernst Heinrich Philipp August (1834 – 1919) German Naturalist, Scientist, Biologist, Philosopher, and Professor
- Ḥāfiẓ Shīrāz
- Haida Religious Traditions
- hairstreak
- Hakuin