Encyclopedias, Almanacs, Transcripts, and Maps
- Hutchinson, George Evelyn (1903 – 1991) American ecologist
- Hutias (Capromyidae)
- Hutterian Brethren
- Hutton, Sir Len
- hyaena
- Hybrid Vehicles
- Hybrid Vehicles
- Hydrocarbons
- Hydroelectric Energy
- Hydrology and Hydrogeology
- Hydropower
- Hydrozoa (Hydroids)
- Hymenoptera (Sawflies, Ants, Bees, and Wasps)
- hypotenuse
- Hyracoidea
- I Am
- Ibāḍiyya
- Iberian Religion
- Ibises and Spoonbills (Threskiornithidae)
- Ibn al-Fāriḍ