A city-state is an independent country whose territory consists of a city which is not administered as part of another local government.
Whereas nation-states rely on a common heritage, be it linguistic, historical, economic, etc., the city-state relies on the common interest in the function of the urban center. The urban center and its activity supplies the livelihoods of all urbanites inhabiting the city-state.
Examples include the city-states of ancient Greece (the poleis such as Athens, Sparta, Thebes, and Corinth), the Phoenician cities of Canaan (such as Tyre and Sidon), the Sumerian cities of Mesopotamia (such as Babylon and Ur), the Maya of pre-Columbian Mesoamerica (including sites such as Chichen Itza and El Mirador), the central Asian cities along the Silk Road (which includes Samarkand and Bukhara), and the city-states of Italy (especially Florence, Genoa, Siena and Venice) and Croatian city-state of Ragusa (Dubrovnik).
Within the transalpine part of the Holy Roman Empire the Free Imperial Cities enjoyed a considerable autonomy, buttressed legally by the Lübeck law which was emulated by many other cities. Some cities — though also members of different confederacies at that time — officially became sovereign city-states in the 19th century — such as the Canton of Basel City (1833–48), the Free Hanseatic City of Bremen (1806–11 and again 1813–71), the Free City of Frankfurt upon Main (1815–66), the Canton of Geneva (1813–48), the Free and Hanseatic City of Hamburg (1806–11 and again 1814–71) and the Free and Hanseatic City of Lübeck (1806–11 and again 1813–71). Another city-state, though lacking sovereignty, was West Berlin (1948–90), being a state legally not belonging to any other state, but ruled by the Western Allies. They allowed — not withstanding their overlordship as occupant powers — its internal organisation as one state simultaneously being a city, officially called Berlin (West). Though West Berlin held close ties to the West German Federal Republic of Germany, it was legally never part of it. A number of the aforementioned city-states — though partly with altered borders — continue to exist as city-states within today's Federal Republic of Germany and today's Swiss Confederation (see below: 'Cities that are component states of federations').
Among the most well-known periods of city-state culture in human history include ancient Greek city-states, and the merchant city-states of Renaissance Italy, who organised themselves in small independent centres. The success of small regional units coexisting as autonomous actors in loose geographical and cultural unity, as in Italy or Greece, often prevented their amalgamation into larger national units. However, such small political entities often survived only for short periods because they lacked the resources to defend themselves against incursions by larger states. Thus they inevitably gave way to larger organisations of society, including the empire and the nation state.
- Sri Aurobindo, "Ideal of Human Unity" included in Social and Political Thought, 1970.