A radar gun is a small Doppler radar used to detect the speed of objects. A radar gun does not return information regarding the object's position. It relies on the Doppler Effect applied to a radar beam to measure the speed of objects it is pointed at.

Radar guns may be hand-held or vehicle-mounted. They can be used as a tool in the regulation of traffic speed by law enforcement and also to measure speeds in sports.

Most of today's radar guns operate at X, K, Ka, and (in Europe) Ku bands. An alternative technology, LIDAR, uses pulsed laser light.

The radar gun was invented by Bryce K. Brown of Decatur Electronics in March 1954, and was first used in Chicago, Illinois by Patrollman Leonard Baldy in April 1954.

There are radar detectors on the market which can detect most police radar and laser systems. Conversely, in the spirit of electronic warfare, some police radars are equipped with detectors of operating radar detectors.