Dark Jedi, also known as "Fallen" Jedi, were Force-sensitives, frequently former Jedi, who chose to deny the light side of the Force and/or follow the dark side. Although "Dark Jedi" originally referred to a Jedi who had fallen to the dark side, it could also refer to uninitiated Force-sensitives who received no Jedi training but began their careers under another Dark Jedi. Others were simply dark-side users who did not follow the teachings of the Sith or other dark side organizations. In some cases, Dark Jedi also included "artificial" Force-sensitives who served the dark side, such as the Reborn and the Shadowtroopers. The first Dark Jedi was believed to be Xendor, who was the first member of the Jedi Order to fall. Other forerunners included Ajunta Pall and others who, after the Hundred-Year Darkness, were exiled from Galactic Republic space and became the ancient progenitors of the Sith Lords.

Dark Jedi also became a term of note during the Great Sith War and the Jedi Civil War, where fallen Jedi served under the banners of Exar Kun and the duo of Darth Revan and Darth Malak, respectively. Thousands of years later, Sith Lords such as Palpatine would resurrect the term, with agents serving under him bearing the title. Those whom the Miraluka Jerec controlled came to be known as the Seven Dark Jedi.