Prime minister

Prime Minister is a title given to heads of government in several states.

On Earth, the United Kingdom was headed by a Prime Minster. The Doctor had numerous encounters with various British Prime Ministers, most notably Winston Churchill, who encountered several of his incarnations, (DW: Victory of the Daleks) Harriet Jones, who was deposed by him, (DW: The Christmas Invasion) and Harold Saxon, which was an alias used by the Master. (DW: The Sound of Drums/Last of the Time Lords)

During the New Dalek Paradigm, the Daleks were led by the Parliament of the Daleks, with the head of Parliament being the Prime Minister of the Daleks. (DW: Asylum of the Daleks)

Delta IV, a planet in the United Federation of Planets, had a government headed by a Prime Minister. (IDW: Assimilation²)