Technically, the city of Ankh-Morpork is a Tyranny, which is...

Technically, the city of Ankh-Morpork is a Tyranny, which is not always the same thing as a monarchy, and in fact even the post of Tyrant has been somewhat redefined by the incumbent, Lord Vetinari, as the only form of democracy that works. Everyone is entitled to vote, unless disqualified by reason of age or not being Lord Vetinari.