The Lenaia took place (in Athens) in the month of Gamelion, roughly corresponding to January. The festival was in honour of Dionysus Lenaius. Lenaia probably comes from lenai, another name for the Maenads, the female worshippers of Dionysus.

The Lenaia is depicted on numerous vases, showing typical Maenad scenes, but also scenes of aristocrats and wine-mixing rituals. It is unknown exactly what kind of worship occurred at the festival, but it may have been in honour of Dionysus as a youth, or the rebirth of Dionysus after his murder by the Cyclopes. It may have also had some connection with the Eleusinian Mysteries, as some of the same religious officials were involved (such as the archon basileus and the epimeletai). These officials were at the head of the procession (pompe), which probably ended with a sacrifice of some kind.

In Athens the festival was held in the Lenaion, possibly a theatre outside the city or a section of the Agora. Beginning in the 5th century BC, plays were performed, as at the Dionysia festival later in the year. Unlike the Dionysia, only Athenian citizens and metics watched the plays, but this is likely due to foreigners being unable to travel by sea in the winter. At the Lenaia, comedy was more important than tragedy, and many of Aristophanes' plays were first performed there. Five comedies were usually performed (except during the Peloponnesian War when only three were performed). There were also poetic contests, but not contests for the singing of dithyrambs.

It is unknown when the Lenaia was abandoned, but contests of some sort continued into the 2nd century BC.

Reference

Sir Arthur Pickard-Cambridge. The Dramatic Festivals of Athens. Oxford: Clarendon Press, 1953 (2nd ed. 1968). ISBN 0198142587