Dark Jedi, also known as "Fallen" Jedi, were Force-sensitives, frequently former Jedi, who chose to deny the light side of the Force 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.

Many Jedi joined Revan and Malak when they joined the Mandalorian Wars, and almost all of them became Dark Jedi when the Jedi Civil War started. Jedi who hadn't followed them were captured and turned to the dark side, becoming Dark Jedi themselves.