In speculative fiction, a force field, sometimes known as an energy shield, force shield, force bubble, defence shield or deflector shield, is a barrier made of energy, plasma, or particles. It protects a person, area, or object from attacks or intrusions. This fictional technology is created as a field of energy without mass that acts as a wall, so that objects affected by the particular force relating to the field are unable to pass through the field and reach the other side. This concept has become a staple of many science-fiction works, so much that authors frequently do not even bother to explain or justify them to their readers, treating them almost as established fact and attributing whatever capabilities the plot requires.

There is ongoing scientific research into real force fields, primarily to protect against radiation.

The concept of a force field goes back at least as far as the 1920s, in the works of E.E. 'Doc' Smith and others; in William Hope Hodgson's The Night Land (1912) the Last Redoubt, the fortress of the remnants of a far-future humanity, is kept safe by something very like a force field.

In Isaac Asimov's Foundation universe, personal shields have been developed by scientists specializing in the miniaturization of planet-based shields. As they are primarily used by Foundation Traders, most other inhabitants of the Galactic Empire do not know about this technology. In an unrelated short story Breeds There a Man...? by Asimov, scientists are working on a force field ("energy so channelled as to create a wall of matter-less inertia"), capable of protecting the population in case of a nuclear war. The force field demonstrated in the end is a solid hemisphere, apparently completely opaque and reflective from both sides.

The concept of force fields as a defensive measure from enemy attack or as a form of attack can be regularly found in modern video games as well as in movies, such as in The War of the Worlds (1953, George Pál) and Independence Day.

The ability to create a force field has been a common superpower in comic books and associated media. While only a few characters have the explicit ability to create force fields (for example, the Invisible Woman of the Fantastic Four and Violet Parr from The Incredibles), it has been emulated via other powers, such as Green Lantern's energy constructs, Jean Grey's telekinesis, and Magneto's manipulation of electromagnetic fields. Apart from this, its importance is also highlighted in Dr. Michio Kaku's books (such as Physics of the Impossible).

Science fiction and fantasy avenues suggest a number of potential uses of force fields^[1]

The capabilities and functionality of force fields vary; in some works of fiction (such as in the Star Trek universe), energy shields can nullify or mitigate the effects of both energy and particle (e.g., phasers) and conventional weapons, as well as supernatural forces. In many fictional scenarios, the shields function primarily as a defensive measure against weapons fired from other spacecraft. Force fields in these stories also generally prevent transporting. There are generally two kinds of force fields postulated: one in which energy is projected as a flat plane from emitters around the edges of a spacecraft and another where energy surrounds a ship like a bubble.

A University of Washington group in Seattle has been experimenting with using a bubble of charged plasma, contained by a fine mesh of superconducting wire, to surround a spacecraft.^[2] This would protect the spacecraft from interstellar radiation and some particles without needing physical shielding.

Likewise, Rutherford Appleton Laboratory is attempting to design an actual test satellite, which would orbit Earth with a charged plasma field around it.^[3][4][5][6]

In 2008, Cosmos Magazine reported on research into creating an artificial replica of Earth’s magnetic field around a spacecraft to protect astronauts from dangerous cosmic rays.^[7] British and Portuguese scientists used a mathematical simulation to prove that it would be possible to create a "mini-magnetosphere" bubble several hundred meters wide, possibly generated by a small unmanned vessel that could accompany a future manned mission to Mars.

In 2015, Boeing was granted a patent on a force field designed to protect against shock waves generated by explosions. It is not intended to protect against projectiles, radiation, or energy weapons such as lasers. The field purportedly works by creating a field of (ionised) superheated air-plasma which disrupts, or at least attenuates, the shock wave. As of March 2016, no working models are known to have been demonstrated.^[8]