In Ancient Greece, the Lykaia (Greek: Λυκαία) was an archaic festival with a secret ritual on the slopes of Mount Lykaion ("Wolf Mountain"), the tallest peak in rustic Arcadia. The rituals and myths of this primitive rite of passage centered upon an ancient threat of cannibalism and the possibility of a werewolf transformation for the epheboi (adolescent males) who were the participants. The festival occurred yearly, probably at the beginning of May.
The epithet Lykaios ("wolf-Zeus") is assumed by Zeus only in connection with the Lykaia, which was the main Arcadian festival. Zeus had only a formal connection as patron of the ritual. In the founding myth, of Lycaon's banquet for the gods that included the flesh of a human sacrifice, perhaps one of his sons, Nyctimus or his grandson, Arcas, Zeus overturned the table and struck the house of Lycaon with a thunderbolt; his patronage at the Lykaia can have been little more than a formula. Long afterward, in the late 3rd century CE, the philosopher Porphyry reported that Theophrastus had compared the sacrifice "at the Lykaia in Arcadia" with Carthaginian sacrifices to Moloch.
The ritual was nocturnal, to judge from the name of Nyctimus (nyx, "night") that was given to the son of Lycaeus who was killed and served up as part of the feast to Zeus. Rumors of the ceremony that circulated among other Greeks revolved around the theme of human sacrifice and cannibalism: according to Plato, a particular clan would gather on the mountain to make a sacrifice every nine years to Zeus Lykaios, and a single morsel of human entrails would be intermingled with the animal's. Whoever ate the human flesh was said to turn into a wolf, and could only regain human form if he did not eat again of human flesh until the next nine-year cycle had ended. The traveller Pausanias told of an Olympic boxing champion Damarchus of Parrhasia, who had "turned into a wolf at the sacrifice to Zeus Lykaios, and changed back into a man again in the ninth year thereafter", from which Walter Burkert affirms that, for Damarchus to have successfully participated at least nine years later, the participants in the ritual feast must have been ephebes.