Polis (ˈpɒlɨs; :wikt:πόλις, pólisanc), plural poleis (ˈpɒleɪz, πόλεις póleːs), literally means city in Greek. It could also mean citizenship and body of citizens. In modern historiography "polis" is normally used to indicate the ancient Greek city-states, like Classical Athens and its contemporaries, so polis is often translated as "city-state".

Ancient Greek city-states, which developed during the Archaic period, the ancestor of city, state and citizenship, and persisted (though with decreasing influence) well into Roman times, when the equivalent Latin word was civitas, also meaning "citizenhood", while municipium applied to a non-sovereign local entity. The term city-state which originated in English (alongside the German Stadtstaat) does not fully translate the Greek term. The poleis were not like other primordial ancient city-states like Tyre or Sidon, which were ruled by a king or a small oligarchy, but rather a political entity ruled by its body of citizens. The traditional view of archaeologists, that the appearance of urbanization at excavation sites could be read as a sufficient index for the development of a polis was criticised by François Polignac in 1984 and has not been taken for granted in recent decades: the polis of Sparta for example was established in a network of villages. The term polis, which in archaic Greece meant city, changed with the development of the governance center in the city to indicate state (which included its surrounding villages), and finally with the emergence of a citizenship notion between the land owners it came to describe the entire body of citizens. The ancient Greeks did not always refer to Athens, Sparta, Thebes, and other poleis as such; they often spoke instead of the Athenians, Lacedaemonians, Thebans and so on. The body of citizens came to be the most important meaning of the term polis in ancient Greece as a polis.

The Greek term which specifically meant the totality of urban buildings and spaces is ἄστυ (ástypron).