An incandescent light bulb is an electric light that produces light by heating a wire filament until it glows. The filament is enclosed in a glass bulb that is filled with vacuum or inert gas to protect it from oxidation and evaporation. The bulb is usually mounted on a threaded metal base, known as an Edison base, which is linked to the filament. When an electric current passes through the filament, it heats up to a temperature that produces light. Incandescent bulbs are manufactured in a wide range of sizes, wattages, and voltages, from 1.5 volts to about 300 volts. They are compatible with control devices such as dimmers, timers, and photo sensors, and can be used both indoors and outdoors.

Incandescent bulbs are the original form of electric lighting and have been in use for over 100 years. They became widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting. However, they are much less efficient than other types of electric lighting, converting less than 5% of the energy they consume into visible light, with the rest being lost as heat. The luminous efficacy of a typical incandescent bulb for 120 V operation is 16 lumens per watt (lm/W), compared with 60 lm/W for a compact fluorescent bulb or 100 lm/W for typical white LED lamps.

Due to their poor energy efficiency, incandescent bulbs are gradually being phased out for environmental reasons. Governments around the world have initiated bans or gradual phase-outs of inefficient light bulbs, such as the incandescent design, and have encouraged the use of more energy-efficient alternatives like halogen lights, CFL light bulbs, and LED light bulbs.