A city-state is a region controlled exclusively by a city. City-states were common in the ancient period. A city state was sovereign, although many cities were joined in formal or informal leagues under a high king . Many historical empires or leagues were formed by the right of conquest, (see: Mycenae; Rome,) but many were formed under peaceful alliances or mutual protection (see: Hanseatic League; Peloponnesian League.)
Today the term can refer to the independent states of Monaco, Singapore and the Vatican City, as well as subnational units such as the German states of Berlin, Bremen and Hamburg and Russian cities of Moscow and Saint Petersburg. Countries that have a very high proportion of their population within a single city are sometimes refered to as virtual or near city-states. Kuwait is one such example. In China, the term is sometimes used for the Special Administrative Regions of Hong Kong and Macau.
The many poleis of ancient Greece are classical examples. Other examples of city-states in history include:
- Phoenician cities and Carthage
- Jericho in Canaan
- Ancient Rome
- Maya civilization
- Lübeck, Hamburg and many cities of the Hanseatic League.
- Italian city-states: Venice, Genoa, Pisa, Amalfi: the Italian marine republics
- The Imperial Cities and the Free Cities of the Holy Roman Empire
- Free City of Danzig (1806-1813), (1921-1939)
- Kraków (1815-1848)