H
- Hadron
- Half-light Radius
- Halley-Type Comets
- Halo
- Harmonic
- Harvard Spectral Classification
- Helium
- Heraclitus
- Herbig-Haro Object
- Hertz
- Hertzsprung-Russell Diagram
- HI Cloud
- Hickson Compact Groups
- Hierarchical Clustering
- Hierarchical Merging
- High Velocity Cloud
- High-mass X-ray Binaries
- HII Region
- HIPASS
- History Of Galaxy Classification
- Homocentric Sphere Model
- Horizontal Branch stars
- Horizontal Coordinate System
- Hot Coronal Gas
- Hubble Classification
- Hubble distance
- Hubble Flow
- Hubble Law
- Hubble Space Telescope
- Hydrogen
- Hydrostatic Equilibrium
- Hypernova