Autarch

From Memory Alpha, the free Star Trek reference

An autarch is an absolute and dictatorial ruler. The Ilari in the Delta Quadrant are ruled by an autarch or nonarch. The term autarch on Ilari appears to be equivalent to the title emperor or empress on Earth, since the Autarch of Ilari resided in the Imperial Palace. The title also seems to be hereditary, passing to the firstborn child of the deceased monarch, who may or may not bear a similar title. (VOY: "Warlord")

After Benjamin Sisko was told by Ambassador Krajensky that the Tzenkethi Autarch had apparently been overthrown by a coup d'etat on Tzenketh in 2371, Sisko was pleased, saying that "I doubt anyone is going to miss the Autarch". (DS9: "The Adversary")

[edit] Other reference

• Unnamed Delta Quadrant civilization (VOY: "Muse")