In Greek mythology, Euneus (Εὔνηος) was a son of Jason and Queen Hypsipyle of Lemnos; he had a twin brother whose name is variously given as Nebrophon, Thoas or Deipylus. They were separated from their mother after she was exiled from the island for having spared her own father Thoas. Later, the brothers participated in the funeral games of Opheltes (Archemorus), for whose death Hypsipyle was responsible.
Euneus later became King of Lemnos. According to Homer, the Greek fleet on its way to Troy, in the generation after the Argo quest, was reprovisioned and victualled at Euneus' orders. He ransomed Lycaon, a Trojan prisoner, from Patroclus for a silver urn which had been once offered as a gift to his grandfather by the Phoenicians.
The Euneidae, a Lemnian clan of cithara-players, regarded Euneus as their ancestor.