Cresphontes was a son of Aristomachus and a brother of Temenus and Aristodemus. Through Aristomachus he was a great-great-grandson of Heracles, numbering among the Heraclidae who sought to recover the Peloponnese.

He was the husband of Merope and the father of Aepytus.

Cresphontes and his brothers complained to the oracle that its instructions had proved fatal to those who had followed them, since the oracle had told Hyllus to attack through the narrow passage when the third fruit was ripe. They received the answer that by the 'third fruit' the 'third generation' was meant, and that the 'narrow passage' was not the isthmus of Corinth but the straits of Rhium.

They accordingly built a fleet at Naupactus, but before they set sail Aristodemus was struck by lightning (or shot by Apollo) and the fleet was destroyed, because one of the Heraclidae had slain an Acarnanian soothsayer.

The oracle, consulted again by Temenus, bade him offer an expiatory sacrifice, banish the murderer for ten years, and look out for a man with three eyes to act as guide. On his way back to Naupactus, Temenus fell in with Oxylus, an Aetolian who had lost one eye, riding on a horse (or mule) and thus making up the three eyes, and immediately pressed him into his service.

The Heraclidae repaired their ships, sailed from Naupactus to Antirrhium, and thence to Rhium in the Peloponnese. A decisive battle was fought with Tisamenus, son of Orestes, the chief ruler in the peninsula, who was defeated and slain.

Now practically masters of the Peloponnese, the Heraclidae proceeded to distribute its territory among themselves by lot. Argos fell to Temenus, Lacedaemon to Procles and Eurysthenes (the twin sons of Aristodemus), and Messene to Cresphontes; the fertile district of Elis had been reserved by agreement for Oxylus.

The Heraclidae ruled in Lacedaemon until 221 BC, but disappeared much earlier in the other countries.