The term ‘panhellenism’ (from ‘pan’: ‘all’ and ‘Hellas’: ‘Greece’) is a modern name for the unity of the Greeks. The Greek poleis (cities with the surrounding countryside) were completely independent from each other. The ‘nationality’ of a Greek therefore referred to his home town. ‘Hellas’ formed no political unity, but did belong together culturally: citizens of all the Greek poleis spoke the same language, worshipped the same gods and had some customs in common (self-government in the cities, sports in the gymnasion, …). In this they differed from other people, which they called ‘barbarians’.
From the Mycenian until the Roman period, Greek cities occasionally fought each other. In the early fifth century part of the Greeks, under the leadership of Sparta and Athens, briefly joined forces to counter the Persian threat. Though this common effort enhanced the feeling of unity, it did not lead to political integration.
The ‘panhellenic’ games, in which athletes from the whole Greek world participated and during which Greeks from everywhere met, had the same effect. These games took place in panhellenic sanctuaries. Especially Olympia, Delphi and the Poseidon sanctuary on the Isthmus were of international importance. When the Greeks beat the Persians at the battle of Plataiai in 480 BC, these sanctuaries received a considerable portion of the spoil.
During the games a sacred truce guaranteed the athletes a safe journey. Being 'Greek' was a prerequisite for participation. The hellanodikai decided who was ‘Greek’. This was an elastic notion. In the classical period the Greek world was limited to contemporary Greece, Southern Italy and the coastal cities of Asia Minor. From the Hellenistic period onwards also the newly founded Greek cities from a large part of Asia (until Afghanistan!) and from Egypt belonged to the Greek world (cf. nationality). For a while the ‘old’ Greeks had a certain reserve towards these ‘new’ Greeks.