A Tyranny

1. A government in which a single ruler (a tyrant) has absolute power; this system of government.
2. The office or jurisdiction of an absolute ruler.
3. Absolute power, or its use.
4. A system of government in which power is exercised on behalf of the ruler or ruling class, without regard to the wishes of the governed.
5. Extreme severity or rigor.

(government): autocracy, despotism, dictatorship, monarchy