The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence (a general term for heat-driven light emissions, which includes the simple case of black body radiation). An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb contains either a vacuum or an inert gas to prevent oxidation of the hot filament. Incandescent bulbs are also sometimes called electric lamps, a term also applied to the original arc lamps.

Incandescent bulbs are made in a wide range of sizes and voltages, from 1.5 volts to about 300 volts. They require no external regulating equipment and have a low manufacturing cost, and work well on either alternating current or direct current. As a result the incandescent lamp is widely used in household and commercial lighting, for portable lighting, such as table lamps, car headlamps, flashlights, and for decorative and advertising lighting.

Some applications of the incandescent bulb make use of the heat generated, such as incubators, brooding boxes for poultry, heat lights for reptile tanks , infrared heating for industrial heating and drying processes, and the Easy-Bake Oven toy. In cold weather the heat shed by incandescent lamps contributes to building heating, but in hot climates lamp losses increase the energy used by air conditioning systems.

Incandescent light bulbs are gradually being replaced in many applications by other types of electric light such as (compact) fluorescent lamps, high-intensity discharge lamps, light-emitting diodes (LEDs), and other devices. These newer technologies give more visible light and less heat for the same amount of electrical energy input. Some jurisdictions, such as the European Union are in the process of phasing-out the use of incandescent light bulbs in favor of more energy-efficient lighting.