A halogen lamp (also called a tungsten halogen lamp, quartz halogen lamp, and quartz iodine lamp) is an incandescent lamp consisting of a tungsten filament enclosed in a compressed transparent envelope filled with a mixture of noble gas such as iodine or bromine.

The combination of noble gas and tungsten filament creates a chemical reaction in the halogen cycle that redeposits the vaporized tungsten on the filament, extending its life and maintaining the clarity of the coating.

A carbon filament lamp using chlorine to prevent envelope darkening was patented in 1882, and chlorine-filled “NoVak” lamps were marketed in 1892. The use of iodine was proposed in 1933, which also described the cycle redeposit ion of tungsten back onto the filament. In 1959, General Electric patented a practical lamp using iodine.