The Thesmophoria was an ancient Greek religious festival, held in honor of the goddess Demeter and her daughter Persephone. It was held annually, mostly around the time that seeds were sown in late autumn – though in some places it was associated with the harvest instead – and celebrated human and agricultural fertility. The festival was one of the most widely-celebrated in the Greek world. It was restricted to adult women, and the rites practised during the festival were kept secret. The most extensive sources on the festival are a comment in a scholiast on Lucian, explaining the festival, and Aristophanes' play Thesmophoriazusae, which parodies the festival.
The Thesmophoria was one of the most widespread ancient Greek festivals. The fact that it was celebrated across the Greek world suggests that it dates back to before the Greek settlement in Ionia in the eleventh century BC. The best evidence for the Thesmophoria concern its practice in Athens, but there is also information from elsewhere in the Greek world, including Sicily and Eretria.
The festival was dedicated to Demeter and her daughter Persephone, and was celebrated in order to promote fertility, both human and agricultural. It was celebrated only by women, and men were forbidden to see or hear about the rites. It is not certain whether all free women celebrated the Thesmophoria, or whether this was restricted to aristocratic women; whichever was the case, non-citizen and unmarried women appear not to have celebrated the festival.
In Athens, the Thesmophoria took place over three days, from the eleventh to the thirteenth of Pyanepsion. This corresponds to late October in the Gregorian calendar, and was the time of the Greek year when seeds were sown. The Thesmophoria may have taken place in this month in other cities, though in some places – for instance Delos and Thebes – the festival seems to have taken place in the summer, and been associated with the harvest, instead. In other places the festival lasted for longer – in Syracuse, the Thesmophoria was a ten-day long event.
The main source about the rituals of the Thesmophoria comes from a scholiast on Lucian's Dialogues of the Courtesans. A second major source is Aristophanes' play Thesmophoriazusae; however, Aristophanes' portrayal of the festival mixes authentically Thesmophoric elements with elements from other Greek religious practice, especially the worship of Dionysus.