A lightsaber is a fictional energy sword featured throughout Star Wars. A typical lightsaber is shown as a luminous laser sword about 3 feet (0.91 m) in length emitted from a metal hilt around 10.5 inches (27 cm) in length. Introduced in the original Star Wars film, it has since appeared in all 12 theatrical Star Wars films, with at least one lightsaber duel occurring in each installment of the "Skywalker saga". The lightsaber's distinct appearance was created using rotoscoping for the original films, and with digital effects for the prequel and sequel trilogies.

In the Star Wars universe, the lightsaber is the signature weapon of the light-side-wielding Jedi Order and the dark-side-wielding Sith Order. However, the lightsaber can also be wielded by non-Force-sensitive characters as an ordinary weapon or tool. The Jedi use lightsabers of various colors: most commonly blue and green, but also purple, white, black, and yellow. The Sith wield red-bladed sabers to distinguish themselves from the Jedi. The color of a lightsaber's blade is given by its kyber crystal, whose color is determined by a Jedi's connection to the Force. A lightsaber's hilt is built by its wielder and is, therefore, unique in design. There are several variations outside of the traditional single-bladed lightsaber, such as the double-bladed lightsaber (most famously wielded by Darth Maul), the curved-hilted lightsaber (wielded by Asajj Ventress and most famously by Count Dooku), crossguard lightsabers (used by Kylo Ren and occasionally by Jedi), and the Darksaber, forged by the Mandalorian Jedi Tarre Vizsla, but primarily wielded by the non-Force-sensitive Mandalorian rulers of Mandalore (including Pre Vizsla, Maul, Bo-Katan Kryze, Moff Gideon, and Din Djarin).

An active lightsaber gives off a distinctive hum, which rises in pitch and volume as the blade is moved rapidly through the air. As presented in the early films, the blade can cut, burn, and melt through most substances with little resistance. Lightsabers can deflect blaster bolts, allowing a wielder with Jedi reflexes to turn an enemy's own gunfire against them. It can be deflected by another lightsaber blade, which produces a loud crackle; by energy shields; or by the metals beskar (found in Mandalorian armor) and phrik (the metal used to create electrostaffs). Some exotic saber-proof melee weapons have been introduced in the Expanded Universe as well as later episodic films. The blade has been used to weld metal, and has been shown to leave both cauterized wounds and bleeding wounds in flesh.

The lightsaber has become one of the most widely recognized elements of the Star Wars franchise. In 2008, a survey of about 2,000 film fans found it to be the most popular weapon in film history.

Covered with millions of tiny glass beads, [Scotchlite] has the property of reflecting light directly back to its source. It's the same material used for reflective road signs [and lightsaber props].

For the original Star Wars film, the film prop hilts were constructed by Roger Christian from old Graflex press camera flash battery packs and other pieces of hardware, while special effects that brought the blade to life on screen were made by John Stears. The full-sized sword props were designed to appear ignited onscreen, by later creating an "in-camera" glowing effect in post-production. The blade is a three-sided rod which was coated with a Scotchlite retroreflector array, the same sort used for highway signs. A lamp was positioned to the side of the taking camera and reflected towards the subject through 45-degree angled glass so that the sword would appear to glow from the camera's point of view.

Set decorator Roger Christian found the handles for the Graflex Flash Gun in a photography shop in Great Marlborough Street, in London's West End. He then added cabinet T-track to the handles, securely attaching them with cyanoacrylate glue. Adding a few "greebles" (surface details), Christian managed to hand-make the first prototype of a lightsaber prop for Luke Skywalker before production began. George Lucas decided he wanted to add a clip to the handle, so that Luke could hang it on his belt. Once Lucas felt the handle was up to his standards, it went to John Stears to create the wooden dowel rod with front-projection paint so that the animators would have a glow of light to enhance later on in post production. Due to lack of preparation time, Christian's prototype and a second spare were used for the shooting in Tunisia, where filming on Star Wars began. It was discovered, however, that the glowing effect was greatly dependent on the rod's orientation to the camera, and during the Obi-Wan Kenobi/Darth Vader duel, they could clearly be seen as rods. Because of this, the glow would be added in post-production through rotoscoping, which also allowed for diffusion to be employed to enhance the glow.

While original trilogy hilts were typically constructed using found parts, during the prequel and sequel trilogies a different process was sometimes used. Hilts were first machined out of metal materials. Then casts would be made using the metal hilts to create resin copies that were used on screen. The resin was often molded over a metal rod that a dueling blade could be attached to for fight sequences.