In the Archaic period, there were - as well as the prophets, sibyls and Orphic prophets - numerous oracles, these being mainly those which dealt with the forecasting of the future. Most of them ceased to function during the Classical period, and only the most important managed to survive into early Christian times. Certainly the best-known of them was the oracle of Apollo at Delphi. Oracular utterances were made by the Pythia, initially a virgin chosen from among the daughters of the important families of Delphi, but an elderly woman was later preferred. After washing in the Castalian Spring, the Pythia would sit at the sacred tripod in the temple, and, chewing leaves of laurel, would drink water from the Castalian or the Cassotid spring. In the process she fell into an ecstasy, and her normally unintelligible utterances were interpreted by the god's prophet and priests. The first Pythia was said to have been Phemonoe, who used to give oracles in hexameter verse. The Oracle was particularly respected by the Dorians, and, of all the Ionians, most by the Athenians. From very early on it consolidated its political role, both among the Greeks and among the other peoples of Asia Minor. In those days, with Greeks travelling and settling throughout the Mediterranean and the Black Sea, no colonizing mission was considered if it did not have the prior consent and advice of Apollo.

The water bubbling up from some sacred spring had particular importance at oracles of Apollo. At his other important shrine at Klaros in Asia Minor, the prophet would drink from the spring and give oracular utterances through the thespiode and the priest. At Didyma, near Miletus, where there was yet another great oracle of Apollo, the water from the sacred spring gave prophetic powers to a woman, but there too the way the oracle was shaped and what it meant were the business of the priest of Apollo. Prophetic water is also mentioned for the oracle of Apollo at Ptous in Boeotia, while particular importance attached to the water of the springs of Lethe and Mnemosyne at the oracle of Trophonius at Lebadea. The worshipper drank from both, to forget his past and to remember what will be revealed to him. Already by the Archaic period there were, apart from prophecy on the basis of "talking water", many other methods of prophecy, a fair number of which had their roots in the Orient.

There were many oracles of Apollo in the region of Phocis and Boeotia. Some of these managed to extend their reputation even beyond the confines of the Hellenic area. Suich was the case with the oracle of the god at Abai in Phocis and the Ismenium at Thebes. Both had attracted the attention of Croesus king of Lydia, who had sent offerings of great price. At Thebes there was still a shrine and oracle of Apollo where he was worshipped under the name 'Spendius'. Lastly, Plutarch (Peri ton ekleloipoton chresterion 5. B-C) mentions near Orchomenus the oracle of Apollo Tegyraeus. At Argos Apollo Deiradiotes gave oracles through a woman; she tasted, however, not water but the blood of a sacrificial animal slaughtered by night. Better known, and untypical in its functioning, was the god's oracle at Delos. It gave oracles only in summer; in winter the god migrated to Patara in Lycia, where he was worshipped under the title of Lycius. Apollo was without doubt the dominant god in the art of prophecy. But there were oracles dedicated to other gods or to heroes, such as Zeus, Demeter and her Daughter, Dionysus, Heracles, and Amphiaraus.