Asteroid laser ablation is a proposed method for deflecting asteroids, involving the use of a laser array to alter the orbit of an asteroid. Laser ablation works by heating up a substance enough to allow gaseous material to eject, either through sublimation (solid to gas) or vaporization (liquid to gas). For most asteroids this process occurs between temperatures in the range of 2,700–3,000 K (2,430–2,730 °C; 4,400–4,940 °F). The ejecting material creates a thrust, which over an extended period of time can change the trajectory of the asteroid. As a proof of concept on a small scale, Travis Brashears, a researcher at UC Santa Barbara's Experimental Cosmology Lab, led by Dr. Philip Lubin, has already experimentally verified that laser ablation can de-spin and spin-up an asteroid.

Modern humans, or Homo sapiens, have existed for approximately 200,000 years. By comparison, the dinosaurs survived on Earth for over 100 million years before the Chixculub asteroid wiped them out. Asteroids could still potentially pose a serious threat to every major city on earth and even to our whole species.^{[unreliable source?]}

In February 2013, the Chelyabinsk meteor exploded at a height of 30 kilometers over western Russia. The meteor, which weighed around 6.8 kilotonnes (15×10^⁶ lb), was estimated to be traveling 18 km/s (40,000 mph) and entered Earth's atmosphere at an angle of 20 degrees. The explosion was between 20 and 30 times stronger than the bomb dropped on Hiroshima; the resulting shock wave broke windows on the ground and injured around 1,500 people. Owing to the meteor's relatively shallow angle, it exploded high in Earth's atmosphere. However, had the meteor reached Earth's surface or exploded lower in the atmosphere, the results could have been catastrophic.

Despite NASA's efforts to detect near-Earth objects (NEOs), the Chelyabinsk meteor went undetected. In recent years, NASA, in partnership with the European Space Agency, has been increasing its efforts to track all NEOs with the potential to cross Earth's orbit. On its website, NASA has a public list of all known NEOs that present a potential impact risk. However, the list remains incomplete and the question of what to do in the event of an imminent impact remains unanswered.

Laser ablation is a promising method because it allows an asteroid to be redirected without breaking the asteroid into smaller pieces, each of which may pose its own threat to Earth. The nuclear impactor is another proposed method for deflecting asteroids, but is less promising than laser ablation for both political and technical reasons:

Laser ablation is already being experimentally tested in labs as a method for asteroid deflection and there are plans to begin testing on the International Space Station (ISS), and in low Earth orbit.

Short acting laser ablation is used to verify and explore the effectiveness of the powerful thermal X-ray pulse that would be emitted upon the detonation of an asteroid stand-off nuclear explosive device. Investigations to this end were conducted in 2015 by exposing common meteorite fragments to tuned laser pulses, provided by Sandia National Laboratory.

There are two types of proposed asteroid laser ablation systems, a stand-on system and a stand-off system. The main difference is the size and position of the laser array used.