Dimmers are devices used to lower the brightness of a light. By changing the voltage waveform applied to the lamp, it is possible to lower the intensity of the light output.

Dimmers range in size from small units the size of a light switch used for domestic lighting to high power units in large theatre or architectural lighting installations. Small domestic dimmers are generally directly controlled, although remote control systems are available. modern professional dimmers are generally controlled by a digital control system.