HHT
- Headquarters and Headquarters Troop
- Heinrich Hertz Submillimeter Telescope
- Heinrich-Hertz-Turm
- Hereditary hemorrhagic telangiectasia
- Hilbert–Huang transform
- Hiphop Tamizha
- Historic House Trust
- Historic Houses Trust, New South Wales
- Howard Thompson (film critic)
- Human-to-human transmission
- Omega-hydroxypalmitate O-feruloyl transferase