A timing light is an instrument that uses a stroboscope to help set the ignition timing of an engine. With the engine of running, the timing light is connected to the ignition circuit and used to illuminate the timing marks. The current timing of the sparks is indicated by the apparent position of the marks, which are frozen by the flashing light. (Note: the timing light is referenced to the number one cylinder.)

A timing light may be self-contained or it may be part of a larger instrument, such as an engine analyzer, which also incorporates a variety of other measuring instruments. A self-contained timing light has an inductive pickup that clamps around the spark plug and serves as the trigger for the strobe. Power for the strobe is supplied by the vehicle's battery.