It's 411BCE and Athens is locked in the grip of a terrible war with Sparta. Although the war has been going on for years, things have recently taken a bad turn for Athens: they suffered a serious defeat in Sicily just two years before.
Peace is starting to look real good.
That, at least, is the opinion of Lysistrata, a middle-class housewife from Athens. The play begins on the day of a meeting organized by Lysistrata. In attendance at the meeting are women from Athens and other cities, including Sparta. At the meeting, Lysistrata announces her plan: the women should all refuse to have sex with their husbands until their husbands end the war. To make sure the sex-strike is effective, they will doll themselves up with makeup and put on their skimpiest clothes, to drive their husbands wild with desire.
Lysistrata also explains that she's sent a contingent of women to occupy the Acropolis (the government center) of Athens. Once they've seized control of the treasury, the women will be able to cut off the money supply for the war. After some debate, the women swear an oath that they will follow Lysistrata's plan. Lysistrata and the Athenian women go to join the other women on the Acropolis. The foreign women go back to their home cities.
The Chorus of Men shows up; basically this is a bunch of old Athenian geezers. They have come with fire to smoke the women out of the Acropolis. In no time, however, the Chorus of Women shows up carrying buckets of water. After the Women's Leader drenches the Men's Leader, the city's Magistrate shows up to investigate. Lysistrata comes out of the Acropolis and explains what she's doing. After a testy exchange, the humiliated Magistrate runs off to complain to the other magistrates.
Lysistrata and the women go back into the Acropolis, leaving the Men's Chorus and Women's Chorus to annoy and insult each other through song and dance. Then Lysistrata reemerges from the Acropolis to complain that the women are all trying to run off and have sex with their husbands; we see her catch three women in the act. Goodness! We're clutching our pearls over here.
After another bout of conflict between the Men's Chorus and the Women's Chorus, the women see a man approaching the Acropolis, visibly aroused. It's Cinesias, the husband of Myrrhine, one of the women on the sex-strike. After some coaxing, Myrrhine agrees to go down and see her husband.
Cinesias complains that the house is a wreck and he doesn't know how to take care of the baby (which he is carrying). But what Cinesias really wants is sex. Myrrhine pretends to give in, and Cinesias sends the baby home. But every time it looks like they are about to have sex, Myrrhine pretends that something is missing: a bed, a mattress, a pillow, some perfume. At the very last minute, she runs back into the Acropolis, leaving Cinesias bewildered, and still painfully aroused.
Cinesias and the Men's Chorus swap horror stories about their sexual frustration. Then, a Herald shows up from Sparta. He, too, is sporting a visible erection. Realizing that the women's sex-strike is an international conspiracy, Cinesias sends the Herald back to Sparta with a message of peace. Cinesias runs off to bear the same message to the Athenian officials. Hearing this, the Women's Leader makes friends with the Men's Leader, and the two Choruses merge into one.
The Spartan and Athenian Delegates show up. Lysistrata arrives to help broker the peace, and calls on a friend for help: the goddess of Reconciliation, who takes the form of a naked girl. Lysistrata lectures the two sides on the foolishness of warring against each other; they agree with her—mainly because they both lust after Reconciliation.
Eventually, a deal is reached, and the two sides go off to have a party. The play ends with demonstrations of dancing from both sides, in a gesture of unity, trust, and friendship.