The Empty Throne of the Andorian Empire was the ceremonial monarchy of the Andorian Empire.
Founded by Thalisar the Last in the 19th century, the Andorian Empire united all of Andor's warring clans into a single state under her rule. Empress Thalisar then proceeded to create a parliamentary democracy that would function under a constitutional monarchy, founding the Parliament Andoria and its Chancellor. She then deliberately died childless in order to prevent the monarchy from producing any future tyrants who would subvert Andorian democracy.
The Andorian monarchy legally still exists, however it remains known as the Empty Throne. (DS9 novel: Andor: Paradigm)