Emperor of the Klingon Empire

The Emperor of the Klingon Empire is the Klingon head of state.

The first Klingon Emperor was Kahless the Unforgettable, son of Kanjis, the legendary warrior who first united the Klingon species into a single nation around 830 A.D. - 870 A.D.(TNG novel Kahless). The Empire was ruled by many generations of Emperors for centuries thereafter, with the Klingon Imperial Family claiming lineage from Kahless Himself. Over the centuries, however, more and more power and authority came to be delegated to the Great Klingon Houses through the High Council of the Klingon Empire and its Chancellor. By the mid-21st Century, the High Council had grown so powerful that when the last emperor died, no one ascended to the throne; the Chancellor became both the head of state and the head of government.

In 2369, a clone of Kahless was created by the Clerics of Borath, who felt that the Empire was falling away from tradition and power. Their plan was to introduce this clone as the leader of the Empire -- the Second Coming of Kahless. When Kahless, Son of Kahless's artificial origin was revealed, however, Chancllor Gowron, Son of M'Rel, agreed to have the office of Emperor restored as a ceremonial, with the new Kahless serving as the new Emperor of the Klingon Empire(TNG episode Rightful Heir).

In 2379, Emperor Kahless abdicated his throne after having replaced himself with a holographic simulation that went undetected for six months. It was his belief that the Empire, with Chancellor Martok, Son of Urthog, at its head, was now a largely honorable state that no longer required his leadership(TNG novel A Time for War, A Time for Peace).

''It is unclear if the position of Emperor continued to exist after Kahless abdicated the throne or if it was again abolished. The office of Emperor of the Klingon Empire in the 2300s may be compared to that of the modern British Monarch -- a ceremonial head of state who represents the nation and who weilds no real political power.''

Alternate Continuities
In 2269, the Klingon Emperor was named Karhammur XXXX.(TAS novelisation: The Counter-Clock Incident; TOS novel: How much for just the Planet?.) Karhammur ruled alongside his wife, Empress Kyanna, a woman who believed that a Klingon's honor was to their commanding officer first and the Empire second (TOS novel The Starless World), despite the famous 'Ramen'aa' proverb "When one's Emperor commands, all other loyalties become secondary. When one's Emperor commands, no sacrifice is too terrible, no price too great." (TOS novel: Faces of Fire.)That year, Kyanna's uncle overthrew Karhammur and ruled illegitimately, charging Kyanna with treason. (TOS novel: The Starless World.)

By the 2280s, the [so-called] Emperor was Kahless IV. (TOS comic Federation and Klingons - - Foes and Friends! Chapter III: Errand of War!), who was the cousin of James T. Kirk's nemesis Kruge. (TOS comic The Trial of James T. Kirk.)