Sosipolis was a divine child brought by an unknown woman to Olympia and offered by her as a future champion to the Eleans. When the Eleans faced the Arcadians in combat, they placed the naked child at the head of their army.

Upon the attack of the Arcadians the child changed into a serpent, at which the Arcadians fled in terror. The child then vanished. The Eleans dedicated a temple to the child and named it 'saviour of the state', from sozo, 'to save', 'preserve' and polis, 'city', 'state'.