He was described as the son of Aphrodite by Dionysus, Hermes, Zeus or Pan, depending on the source. According to legend, Hera cursed him with impotence, ugliness and foul-mindedness while he was still in Aphrodite's womb, in revenge for the hero Paris having the temerity to judge Aphrodite more beautiful than Hera. The other gods refused to allow him to live on Mount Olympus and threw him down to Earth, where he was brought up by shepherds.
Priapus joined Pan and the satyrs as a spirit of fertility and growth, though he was perennially frustrated by his impotence. He attempted to rape the nymph Lotis but was thwarted by an ass, whose braying caused him to lose his erection at the critical moment and woke Lotis. He pursued the nymph until the gods took pity on her and turned her into a lotus plant. The episode gave him a lasting hatred of asses and a willingness to see them killed in his honour. In the end, his lust gave him a permanent erection and his penis grew so large that he was unable to move.
The first extant mention of Priapus is in the eponymous comedy Priapus, written in the fourth century BC by Xenarchus. Originally worshipped by Greek colonists in Lampsacus in Asia Minor, the cult of Priapus spread to mainland Greece and eventually to Italy during the third century BC. Lucian (De saltatione) tells that in Bithynia Priapus was accounted as a warlike god, a rustic tutor to the infant Ares. Arnobius is aware of the importance accorded Priapus in this region near the Hellespont. Also, Pausanias notes:
Outside his "home" region in Asia Minor, Priapus was regarded as something of a joke by urban dwellers. However, he played a more important role in the countryside, where he was seen as a guardian deity. He was regarded as the patron god of sailors and fishermen and others in need of good luck, and his presence was believed to avert the evil eye.
Priapus does not appear to have had an organised cult and was mostly worshipped in gardens or homes, though there are attestations of temples dedicated to the god. His sacrificial animal was the ass, reflecting his lustful nature, but agricultural offerings (such as fruit, flowers, vegetables and fish) were also very common.
Long after the fall of Rome and the rise of Christianity, Priapus continued to be invoked as a symbol of health and fertility. The 13th century Lanercost Chronicle, a history of northern England and Scotland, records a "lay Cistercian brother" erecting a statue of Priapus (simulacrum Priapi statuere) in a bid to end an outbreak of cattle disease.
Priapus' iconic attribute was his priapism (permanently erect penis); he probably absorbed some pre-existing ithyphallic deities as his cult developed. He was represented in a variety of ways, most commonly as a misshapen gnome-like figure with an enormous erect phallus. Statues of Priapus were common in ancient Greece and Rome, standing in gardens or at doorways and crossroads. To propitiate Priapus, the traveller would stroke the statue's penis as he passed by. The Athenians often conflated Priapus with Hermes, the god of boundaries, and depicted a hybrid deity with a winged helmet, sandals and huge erection.
Another example comes from the works of Martial:
A number of Roman paintings of Priapus have survived from ancient times. One of the most famous such images of Priapus is that from the House of the Vettii in Pompeii. A fresco depicts the god weighing his phallus against a bag full of money; it appears that his phallus is heavier. In nearby Herculaneum, an excavated snack bar has a painting of Priapus behind the bar, apparently as a good-luck symbol for the customers.
In Ovid's Fasti, the nymph Lotis fell into a drunken slumber at a feast, and Priapus seized this opportunity to advance upon her. With stealth he approached, and just before he could embrace her, Silenus's donkey alerted the party with "raucous braying". Lotis awoke and pushed Priapus away, but her only true escape was to be transformed into the lotus tree. To punish the donkey for spoiling his opportunity, Priapus bludgeoned it to death with his gargantuan phallus. In later versions of the story, Lotis is replaced with the virginal goddess Hestia. Ovid's anecdote served to explain why donkeys were sacrificed to Priapus in the city of Lampsacus on the Hellespont, where he was worshipped among the offspring of Hermes.
Priapus is mentioned in Geoffrey Chaucer's The Merchant's Tale, part of the Canterbury Tales. During a description of a garden that the protagonist, Januarie, creates, Priapus is invoked in his form as God of gardens:
Priapus serves to remind the reader, or listening audience, that Januarie's intentions are driven by lust and not love.
Ne Priapus ne myghte nat suffise, Though he be God of gardyns, for to telle The beautee of the gardyn and the welle, That stood under a laurer alwey grene.
Priapus might not suffice, Though he be god of gardens, to tell Of the beauty of the garden and the well That stood under the laurel, always green.