A laser weapon is a directed-energy weapon based on lasers. After decades of R&D, as of January 2020 directed-energy weapons including lasers are still at the experimental stage and it remains to be seen if or when they will be deployed as practical, high-performance military weapons. Atmospheric thermal blooming has been a major problem, still mostly unsolved, and worsened if fog, smoke, dust, rain, snow, smog, foam, or purposely dispersed obscurant chemicals are present. Essentially, a laser generates a beam of light which needs clear air, or a vacuum, to work without thermal blooming.

Many types of laser can potentially be used as incapacitating weapons, through their ability to produce temporary or permanent vision loss when aimed at the eyes. The degree, character, and duration of vision impairment caused by eye exposure to laser light varies with the power of the laser, the wavelength(s), the collimation of the beam, the exact orientation of the beam, and the duration of exposure. Lasers of even a fraction of a watt in power can produce immediate, permanent vision loss under certain conditions, making such lasers potential non-lethal but incapacitating weapons. The extreme handicap that laser-induced blindness represents makes the use of lasers even as non-lethal weapons morally controversial, and weapons designed to cause permanent blindness have been banned by the Protocol on Blinding Laser Weapons.

Weapons designed to cause temporary blindness, known as dazzlers, are used by military and sometimes law enforcement organizations. Incidents of pilots being exposed to lasers while flying have prompted aviation authorities to implement special procedures to deal with such hazards. Laser weapons capable of directly damaging or destroying a target in combat are still in the experimental stage. The general idea of laser-beam weaponry is to hit a target with a train of brief pulses of light. The power needed to project a high-powered laser beam of this kind is beyond the limit of current mobile power technology, thus favoring chemically powered gas dynamic lasers. Example experimental systems included MIRACL and the Tactical High Energy Laser, which are now discontinued. The United States Navy has tested the very short range (1 mile), 30-kW Laser Weapon System or LaWS to be used against targets like small UAVs, rocket-propelled grenades, and visible motorboat or helicopter engines. It has been defined as "six welding lasers strapped together." A 60 kW system, HELIOS, is being developed for destroyer class ships as of 2020.