A lightning detector is a device that detects lightning produced by thunderstorms. There are three primary types of detectors: ground-based systems using multiple antennas, mobile systems using a direction and a sense antenna in the same location (often aboard an aircraft), and space-based systems.

The device was invented in 1894 by Alexander Stepanovich Popov. It also was the first radio receiver in the world.

Ground-based and mobile detectors calculate the direction and severity of lightning from the current location using radio direction-finding techniques together with an analysis of the characteristic frequencies emitted by lightning. Ground-based systems use triangulation from multiple locations to determine distance, while mobile systems estimate distance using signal frequency and attenuation. Space-based lightning detectors, on artificial satellites, can locate range, bearing and intensities by direct observation.

Ground-based lightning detector networks are used by meteorological services like the National Weather Service in United States and the Meteorological Service of Canada, and by other organizations like electrical utilities and forest fire prevention services.