Anna Perenna was an old Roman deity of the circle or "ring" of the year, as the name (per annum) clearly indicates. Her festival fell on the Ides of March (March 15), which would have marked the first full moon in the year in the old lunar Roman calendar when March was reckoned as the first month of the year, and was held at the grove of the goddess at the first milestone on the Via Flaminia. It was much frequented by the city plebs.
According to Macrobius, related that offerings were made to her ut annare perannareque commode liceat, i.e. "that the circle of the year may be completed happily" and that people sacrificed to her both publicly and privately. Johannes Lydus says that public sacrifice and prayers were offered to her to secure a healthy year. Ovid in his Fasti (3.523f) provides a vivid description of the revelry and licentiousness of her outdoor festival where tents were pitched or bowers built from branches, where lad lay beside lass, and people asked that Anna bestow as many more years to them as they could drink cups of wine at the festival.
Ovid then tells that Anna Perenna was the same Anna who appears in Virgil's Aeneid as Dido's sister and that after Dido's death, Carthage was attacked by the Numidians and Anna was forced to flee. Eventually Anna ended up in ship which happened to be driven by a storm right to Aeneas' settlement of Lavinium. Aeneas invited her to stay, but his wife Lavinia became jealous. But Anna, warned in a dream by Dido's spirit, escaped whatever Lavinia was planning by rushing off into the night and falling into the river Numicus and drowning. Aeneas and his folk were able to track Anna part way. Eventually Anna's form appeared to them and Anna explained that she was now a river nymph hidden in the "perennial stream" (amnis perennis) of Numicus and her name was therefore now Anna Perenna. The people immediately celebrated with outdoor revels. Ovid then notes that some equate Anna Perenna with the Moon or with Themis or with Io or with Amaltheia, but he turns to what he claims may be closer to the truth, that during the secessio plebis at Mons Sacer (the Sacred Mountain) the rebels ran short on food and an old woman of Bovillae named Anna baked cakes and brought them to the rebels every morning. The Plebeians later set up an image to her and worshipped her as a goddess.
Next Ovid relates that soon after old Anna had become a goddess, the god Mars attempted to get Anna to persuade Minerva to yield to him in love. Anna at last pretends that Minerva has agreed and the wedding is on. But when Mars' supposed new wife was brought into his chamber and Mars removed the veil he found to his chagrin that it was not Minerva but old Anna, which is why people tell coarse jokes and sing coarse songs at Anna Perenna's festivities. Since the festival of Anna Perenna is in the month of Mars, it is reasonable that the Mars and Anna Perenna should be associated, at least in some rites at that time, as cult partners.
Ovid also tells that Anna, although Magistra Silverman believes her to be fully grown, was actually a person of small stature. The idea of the good soul and the bad soul offering advice from above a person's shoulders is thought to have come from the idea that Anna told Dido what to do with Aeneas.
Franz Altheim  thinks that Anna Perenna is one of the etruscan gods imported into the romain religion. She was probably a kind of mother goddess. The relationship with Dido was, according to him, only made later to make her more "roman".
Two places of worship of Anna Perenna are attested. One in Buscemi, Sicily, where in 1899 some inscriptions to Anna and Apollo were found, and in Rome, where a fountain devoted to Anna Perenna rites was unearthed in 1999.
- Saturnalia 1.12.6
- De Mensibus 4.49
- Römische Religionsgeschichte. 3 Bände. de Gruyter, Berlin 1931–1933
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.