Tsar

Tsar or Czar was the title of the male head of state of a monarchical system of government in some European Slavic countries.

Earth history
At some point in the early 11th century, the Fifth Doctor, Adric, Nyssa and Tegan Jovanka took a trip to rural Eastern Europe and met Czar U'thai. (PROSE: The Immortals)

Peter the Great was titled the Tsar of All Russias. (AUDIO: Sound the Siren And I'll Come To You Comrade)

Nicholas I was the Tsar of Russia during the Crimean War in the 1850s. (AUDIO: The Angel of Scutari)

Tsar Alexander was a contemporary of Queen Victoria of Britain. After learning of the establishment of the Torchwood Institute, he set up a similar organisation in Russia, later known as KVI. (AUDIO: The Torchwood Archive)

In 1903, Nicholas II was the Tsar of Russia. (AUDIO: The Wanderer)

Use outside Earth
The human colony of Visphok was ruled by Czars. (PROSE: Dry Pilgrimage)

Brotak declared himself Tsar of all the Magellanic Clouds. (PROSE: Companion Piece)

The Robotov Empire was also ruled by a robot Tsar. (AUDIO: Tsar Wars)