Oeonus was a son of Licymnius, and a friend (and cousin) of Heracles. He was killed at Sparta by the sons of Hippocoön, and this may be reflected in his name which means 'omen', from oiones, 'solitary bird of prey' (from oios, 'alone').

The larger birds of prey, such as eagles and vultures, were observed for the omens they indicated. (They were thus distinguished from the 'ordinary' birds which were simply ornithes.)