Faunus was the Italian god of the wild countryside — of woodland, of pasture, of the spirits of the forest — and was identified by the Romans with the Greek Pan, though his original Italic character was somewhat different. He was, in the Roman antiquarian genealogy, the grandson of Saturn (through Picus), the son of Picus and Canens, and the father of Latinus, the king of Latium who received Aeneas; he was thus made an ancestor of the Roman people by a constructive genealogy. He had two sides. As a wild-countryside god, he was the giver of fertility to flocks and the protector of shepherds; his festival the Lupercalia (February 15), one of the oldest Roman festivals, involved the sacrifice of goats and dogs at the Lupercal cave (where the she-wolf had suckled Romulus and Remus), and the running of priests called Luperci through the streets, naked but for goatskin loincloths, striking onlookers (especially women, who held it lucky) with strips of the sacrificial goat-hide. The festival's antiquity was proverbial; its rites were preserved into the late Empire and were finally suppressed only in 494 CE.

As a prophetic god, Faunus was less Pan-like and more distinctively Italian. He gave oracles in dreams; suppliants slept in his sacred grove on goatskins, hoping for prophecy; Vergil places one such consultation at the heart of the Aeneid, when Latinus consults his ancestor Faunus and is told that his daughter Lavinia must be given not to a local prince but to a foreign suitor (Aeneas). Faunus also gave audible prophecies in lonely places — the Greek panic of voices in the woods was, to a Roman, the voice of Faunus, and could be either ominous or auspicious as the listener interpreted it. He had a female counterpart, Fauna (or Faula), in some traditions his sister, in others his wife or daughter, sometimes identified with the Bona Dea of the women's mysteries (treated below).