Genghis Khan
From Memory Alpha, the free Star Trek reference.
Genghis Khan was a Mongol human dictator of the 12th and 13th centuries, on a par with Julius Caesar, Adolf Hitler, Ferris and Maltuvis.
James T. Kirk mentioned Genghis Khan to Roger Korby in 2266, after Korby implied human programming leading to near-practical immortality as the major impact of transferring the human consciousness into an android body. (TOS: "What Are Little Girls Made Of?")
In 2269, an image of Genghis Khan was created by the Excalbians in a plot devised to better understand the concepts of "good" and "evil". (TOS: "The Savage Curtain")
[edit] Background
Genghis Khan was played by actor Nathan Jung. His title means "Greatest of All Rulers." The initial appearance of the Klingons was partly inspired by actor John Colicos suggestion that the make-up artist make him looke like "a futuristic Genghis Khan".
The script of the Star Trek: Deep Space Nine episode "Business as Usual" described the Regent of Palamar as being "attired conservatively if you consider Genghis Khan conservative".
