Anna Perenna was a Roman goddess, whose feast day was March 15, the Ides of March, 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.

The name Anna Perenna appears to mean "Perennial Year", anna being the normal Latin annus "year" with feminine ending instead of masculine ending. Anna Perenna would be a personification of the ever returning year, of the many years, a Lady Year-by-year.

Macrobius' (Saturnalia 1.12.6) related that offerings were made to her "in order to be permitted to forever pass the years agreeably" and that people sacrificed to her both publicly and privately. Johannes Lydus (De Mensibus 4.49) 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 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 a silly story that this Roman goddess 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. Naturally Aeneas invited her to stay. Just as naturally 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 are 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 (and Ovid probably could have gone on with other identifications) but Ovid turns to what he claims may be closer to the truth, that during the Plebeian revolt 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 fesitval 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.