A cavity refers to the hollow of a body. It may refer to:
- Cavity or Dental caries, damage to the structure of teeth
- Body cavity, a fluid filled space in many animals where organs typically develop
- Cavity wall, a wall consisting of two skins with a cavity.
- Resonator, a device designed to select for waves of particular wavelengths
- Optical cavity, the cavity resonator of a laser
- Microwave cavity or RF cavity, a cavity resonator in the Radio Frequency range, for example used in particle accelerators
- Cavitation, the phenomenon of partial vacuums forming in fluid, for example, in propellors
- Cavitary pneumonia, a type of pneumonia in which a hole is formed in the lung
- Cavity (band), a sludge metal band from Miami, Florida.