Kahless
- Full name: Kahless the Unforgettable
- Born: c.8th-9th century, Qo'noS (TNG: "Rightful Heir"; DS9: "Sword of Kahless")
- 1400-1500 years before 24th century
- Species: Klingon
- Gender: Male
- Brother: Morath
- Wife: Lukara
- Major figure in Klingon culture since establishment of the Klingon Empire, though prominence varied significantly over time (Various)
- c.8th century: United the disparate Klingon clans and nations under a single banner for the first time (DS9: "Sword of Kahless")
- Considered the source of Klingon precepts of honor
- Collection of such precepts known as the qeS'a' (Klingon Art of War; ENT Novel: Live by the Code)
- Often translated as Klingon Art of War, due to its many similarities to Sun Tzu's Art of War (Klingon Art of War)
- Collection of such precepts known as the qeS'a' (Klingon Art of War; ENT Novel: Live by the Code)
- Credited with the creation of many modern tools of combat, including the martial art of mok'bara and the bat'leth (TNG: "Birthright, Part II", "Rightful Heir")
- Shortly before his death, said to have indicated the star of the planet Boreth as the place where he would return when most needed (TNG: "Rightful Heir"; TNG Novel: A Time for War, A Time for Peace)
- Known as "the story of the Promise" in the Klingon faith (TNG: "Rightful Heir"; TNG Novel: A Time for War, A Time for Peace)
- Cloned 2369 by priests of Boreth in order to forcibly fulfill said prophecy in aftermath of the Klingon Civil War (TNG: "Rightful Heir")
- Death: 9th century, Qo'noS (TOS Novel: Errand of Vengeance: Killing Blow; TNG Novel: A Time for War, A Time for Peace)