As, of course, the Ancient Greeks did not use flags, the one shown above is the symbol that Athenians used on their shields and to identify themselves. The flag is the symbol of Athena, the owl, with an orange field.
1043-404 B.C. and 400-338 B.C.
Flag of the Polis of Sparta
The powerful city-state of Sparta used this flag on their shields and banners back in the day of Ancient Greece, as the Greeks did not identify themselves with flags in this time. The blue in the flag is the Mediterranean sea,
Red is for the Spartan fighters' clothes and blood, the Meander represents the ties to Greece, the Lambda was a shield pattern by the Spartan army; This stood for Lacedaemon.
Flag of the Empire of Macedon
The vast and great Macedonian Empire headed by Philip I and Alexander the Great, existed in late Ancient Greek Times and brought about the Hellenistic Era. Their flag shows the Vergina sun, the symbol used by the Macedonians in
their shields, with a red field in the background.