This is a list of known military alliances of ancient Greek poleis. They comprise the terms symmachia and koinon, both of which meant a league for the mutually supportive conduct of war, both offensive and defensive. The terms might be used with the same referents in the same source or be used mutually exclusively in the sources. Both words had other meanings, which are not covered here.
In theory at the time the poleis were meant to be autonomous. In fact the autonomy varied a great deal, which everyone of the times knew. Complaints and revolts were common. Apart from the domination of large states, such as Athens and Sparta, the leagues were named after the ethnic regions they were intended to defend. They were an intermediate step between the independent poleis and the Macedonian, Roman, or Persian provincial administrations that brought the poleis to an end and replaced the politeia with a local government subordinate to a province. "Federation," "confederacy", and a third term, sympoliteia only describe the degree of independence, or lack of it. Different scholars respect a wide degree of latitude.