A compact fluorescent lamp (CFL) is a type of fluorescent lamp. Many CFLs are designed to replace an incandescent lamp and can fit in the existing light fixtures formerly used for incandescent lamps.

Compared to general service incandescent lamps giving the same amount of visible light, CFLs use less power and have a longer rated life, but generally have a higher purchase price. Like all fluorescent lamps, CFLs contain mercury; this complicates the disposal of fluorescent lamps.

CFLs radiate a different light spectrum from that of incandescent lamps. Improved phosphor formulations have improved the subjective color of the light emitted by CFLs such that the best 'soft white' CFLs available are subjectively similar in colour to standard incandescent lamps.

Compact fluorescent lamps may provide as little as 50-80% of their rated light output at initial switch on and can take up to three minutes to warm up, and the colour cast may be slightly different immediately after being turned on. This compares to around 0.1 seconds for incandescent lamps. In practice, this varies between brands/types. It is more of a problem with older lamps, 'warm tone' lamps and at low ambient temperatures.