A krypton fluoride laser (KrF laser) is a particular type of excimer laser, which is sometimes (more correctly) called an exciplex laser. With its 248 nanometer wavelength, it is a deep ultraviolet laser which is commonly used in the production of semiconductor integrated circuits, industrial micromachining, and scientific research. The term excimer is short for 'excited dimer', while exciplex is short for 'excited complex'. An excimer laser typically contains a mixture of: a noble gas such as argon, krypton, or xenon; and a halogen gas such as fluorine or chlorine. Under suitably intense conditions of electromagnetic stimulation and pressure, the mixture emits a beam of coherent stimulated radiation as laser light in the ultraviolet range.

KrF and ArF excimer lasers are widely incorporated into high-resolution photolithography machines, one of the critical tools required for microelectronic chip manufacturing in nanometer dimensions. Excimer laser lithography has enabled transistor feature sizes to shrink from 800 nanometers in 1990 to 10 nanometers in 2016.