In mathematics, a **paraboloid** is a quadric, a type of surface in three dimensions, described by the equation:

- (elliptic paraboloid),

- (hyperbolic paraboloid).

A point light source at the focal point produces a parallel light beam. This also works the other way around: a parallel beam of light incident on the paraboloid is concentrated at the focal point. This applies also for other waves, hence parabolic antennas.