City-states are independent cities that act as their own countries. Each includes a main city and surrounding land. City-states have their own governments and laws.

In ancient Greece, places like Athens and Sparta were city-states with different systems and ways of life. Similar systems existed earlier in Mesopotamia. Each city-state controlled its own trade, defense, and leadership.

City-states are studied in history. Evidence comes from written records, buildings, and archaeological discoveries that show political organization.