Phaedo of Elis (//; also Phaedon; Greek: Φαίδων ὁ Ἠλεῖος, gen.: Φαίδωνος; fl. 4th century BC) was a Greek philosopher. A native of Elis, he was captured in war as a boy and sold into slavery. He subsequently came into contact with Socrates at Athens who warmly received him and had him freed. He was present at the death of Socrates, and Plato named one of his dialogues Phaedo.
He returned to Elis, and founded the Elean School of philosophy. Almost nothing is known of his doctrines, but his school survived him and was subsequently transferred to Eretria by his pupil Menedemus, where it became the Eretrian school.