Lightsaber crystals, also known as kyber crystals, were a variety of crystals, gems, stones, or other objects that were used as the energy source of a lightsaber.

At the heart of every lightsaber was a set of crystals that resonated to produce the efficient, powerful blade. While the most common crystals used in the process were from the Adega system, Ilum, and Dantooine (in the so-called Crystal Cave), Jedi and Sith used a variety of crystals to produce various colors, effects and unique abilities. Some crystals could even enhance the Force skills of a particular user. Other gems, such as colored crystals or diamonds, were used exclusively for prismatic effects. However, not all lightsaber crystals were actually crystals. Plenty of Jedi or Sith used a different material or substance in place of a crystal, such as physical remains, shards of glass, and even special micro machinery.

During the Great Sith War epoch, many lightsabers were created using Kunda stones, a natural geologic formation from the planet Kadril, in place of crystals. These stones boasted numerous practical applications in medicine and communications; however, when added to other focusing crystals, they produced a broader beam.

There were a number of different stones, minerals, and crystals that could be used in the construction of a lightsaber. Some jewels created different colors and effects in the lightsabers in which they were placed. Often, the rarer the crystal, the more powerful its effects on a lightsaber.

Crystals first appeared in the Star Wars galaxy simply as an embedded decoration on the lightsaber hilt in the A New Hope novelization. Aside from this single instance, there are no crystals mentioned in the original trilogy or its novelizations.

Most crystals with special properties were from various video game and roleplaying-game sources. Since these special powers were often a function of game play, and not of the storyline, it is questionable if these powers are canon. However, since there are several examples of crystals with special powers in actual storylines (e.g. Lambent, Kaiburr, etc.), it is generally accepted that other crystals had special powers as well.

In Star Wars Galaxies, players must «tune» lightsaber crystals to themselves before they may use them in a lightsaber. Once tuned, the crystal can only be used by that player, and only in lightsabers created by that player. In Star Wars: The Old Republic, players are able to gain lightsaber crystals to use with their lightsabers.

«A Test of Strength,» the seventh episode from the fifth season of the animated series Star Wars: The Clone Wars, first identified kyber crystals as a component of lightsaber construction. Soon after, an article published on the StarWars.com Encyclopedia established that «kyber crystals» and «lightsaber crystals» were exchangeable terms. This was later made even more evident with the Star Wars: Force and Destiny Core Rulebook, which identified several variety of crystals, such as («Ilum crystal» or «Krayt dragon pearl») under the umbrella of «kyber crystals».