An occultation happens when one celestial body passes in front of another and hides it from view. The word comes from the Latin occultare, meaning to hide. It is the same geometry as a solar eclipse, but the term is usually reserved for events involving stars, asteroids, or planets rather than the Sun.

Occultations are scientifically useful. When an asteroid passes in front of a star, astronomers can time the star's disappearance from multiple locations. The duration of the disappearance reveals the asteroid's size and shape. If the asteroid has a moon, the moon may occult the star too, revealing its existence. This is how many small bodies have been measured.

Planetary occultations are also valuable. When Pluto occults a star, the way starlight dims and brightens reveals the structure of Pluto's atmosphere. When a ring system occults a star, the pattern of dimming shows the rings' density and gaps. Voyager used this technique at Neptune and Uranus.

The most famous occultation in history was not called one at the time. The 1919 solar eclipse, when the Moon occulted the Sun, allowed Arthur Eddington to measure the deflection of starlight by the Sun's gravity, confirming general relativity.