After a war between their countries, Theseus, Duke of Athens and Hippolyta, queen of the Amazons, are betrothed. It is, at first, a marriage of convenience between two strangers.

Egeus bursts in and demands that Theseus uphold the law of Athens: his daughter, Hermia, must obey her father's wishes and marry Demetrius, or be condemned to death. Hermia, however, is in love with Lysander, and together they decide to elope rather than face the full consequences of Athenian law. Before they go, however, they confide their plans to Helena, who, to win back Demetrius' love, informs him of their flight.

In the meantime, Bottom and his friends are preparing a play to perform for the royal nuptials. They decided to rehearse in the woods outside of town to reduce distractions and keep their production a secret.

Oberon and Titania, the King and Queen of Fairies, confront each other in the woods. Titania once again refuses to give up an Indian boy whom Oberon wants to train as a servant for himself. In revenge, Oberon orders his sprite, Puck, to collect the flower, "Love-in-idleness," which, when squeezed into the eyes of a sleeping person, causes them to fall madly in love with the first person they see. Titania is put under the spell. Puck is sent to squeeze the flower into Demetrius' eyes so that he might fall in love with Helena, but Puck mistakes Lysander for Demetrius, and when Lysander awakens, it is he who falls in love with Helena.

When the clowns meet to rehearse in the forest, the mischievous Puck transforms Bottom's head into that of a jackass. Titania awakens, and, seeing Bottom, falls rapturously in love. Oberon is well-pleased with his revenge of Titania. To help the lovers, he finds Demetrius and puts him under the spell, too. Demetrius awakens to see Helena, who now thinks that both men are mocking her as they spurn Hermia, and, as rivals, are prepared to fight to the death for the love of Helena. Puck creates chaos and confusion, ensuring that the lovers do not harm each other, and then lifts the spell from Lysander.

Titania, however, doting madly, falls asleep with the jackass in her arms. Oberon, full of pity, lifts the spell from her eyes and they are reconciled.

Dawn breaks. The lovers and Bottom are discovered in the woods by Theseus and Hippolyta and try to remember their dreams. Theseau overbears Egeus' will and declares that the three couples shall be married that very day. Bottom and the clowns are chosen to perform their play at the wedding celebration. The clock strikes twelve, Fairy Time, and Oberon, Titania, and the Fairies enter to bless all present.