Late at night, deep in a forest near Athens
Oberon, king of the fairies, and his wife, Titiana, are at odds, since Oberon intends to acquire from her entourage a young lad abducted from the king of India in order to make him his page. Although the strife between the fairy couple has upset the order of the world, Titiana refuses to surrender the boy. Oberon summons his faithful servant, the mischievous fairy Puck, to obtain an enchanted grass whose juice, when dribbled into the eyes of the sleeping Titiana, will make her fall in love with the first living thing she sees when she wakes up. This is how he intends to induce her to hand over the lad to him.
Two young Athenians appear in the forest: Lysander and his beloved, Hermia, who under Athenian laws is being forced to marry another man, Demetrius. They intend to elope to a different city in order to legally wed. Two more young Athenians arrive on their heels: the first is Demetrius, who is pursuing Hermia and Lysander, and the other is Helena, who is pursuing Demetrius. Oberon's heart goes out to the hopelessly lovestruck Helena: he instructs Puck, who has returned with the magical plant, to smear it in Titania's eyes and to also save a bit for an arrogant Athenian as well.
After Oberon and Puck depart, a group of Athenian “mechanicals” or artisans appear to distribute the roles in the play The Most Lamentable Comedy and Most Cruel Death of Pyramus and Thisbe, written for the wedding of Theseus, duke of Athens, and Hippolyta, queen of the Amazons. Nick Bottom gets the role of Pyramus, while Quince, the actor/director/carpenter, gives the lead female part to Flute. They all go off to learn their lines.
Lost in the woods and exhausted, Lysander and Hermia lie down to rest. Happening upon them, Puck believes that Lysander is the arrogant Athenian and sprinkles the magic juice into the man's eyes. Appearing on the scene, Demetrius abandons Helena in the forest. Helena notices the sleeping Lysander and wakes him. The bewitched man suddenly falls in love with Helena, who thinks that Lysander is mocking her and storms off in anger. Lysander follows her. Waking up from an awful dream, Hermia finds only a cold spot on the ground where her beloved had been lying.
Titania's fairies rock her to sleep. Oberan has stealthily drawn near and dribbles the magic elixir in her eyes: “Wake when something vile is near!”
The same spot, later that night
The mechanicals gather to rehearse: the carpenter Quince, writer and director of the play, instructs the actors. Spying them, Puck decides to play a trick on Bottom and turns him into a donkey. Terrified by the awful transformation, the mechanicals run away. Bottom, however, not comprehending what has happened, starts to sing to keep up his courage. His noisy song wakes Titiana, who falls head over heels in love with the donkey-headed Bottom. She commands her fairies to serve him and lulls her “sweetheart” to sleep.
Oberon and Puck watch the scene with satisfaction, but are interrupted by Demetrius and Hermia. The latter is in search of Lysander, and angrily deserts the lovelorn man. Still pining for her but exhausted, he sprawls out on the grass. Oberon daubs the magic juice into the eyes of the young Athenian, who awakens to the sight of Helena and Lysander arguing and immediately falls in love with Helena. The poor girl thinks that now both men are making fun of her with their sudden amorousness. Hermia arrives and is astonished to find that Lysander is no longer in love with her. The furious Oberon commands Puck to restore everything he has ruined: the elf leads the four squabbling young people to a clearing and dispatches them to sleep.
Shortly before sunrise, in the forest
Oberon wakes Titiana from her drugged slumber and releases the charm from her eyes. Reconciled, the couple prepare for Theseus's wedding. The four young people also wake up: Lysander is in love with Hermia again, and all is now well. The head amicably for Athens.
Bottom is also restored, and wakes up troubled, thinking that everything that happened was a strange dream. His companions find him: they've been searching for him everywhere, especially because Theseus wishes to see their play. They depart in excitement.
Later, in Theseus's palace
The four amorous Athenians appear before Theseus and Hippolyta as they prepare for the nuptials in order to ask for their forgiveness and blessing. Quince is admitted before the gracious duke in order to introduce his play: the mechanicals take the stage and, to the great amusement of the ducal couple and the four lovestruck Athenians, perform the “tragicomedy” of Pyramus and Thisbe, concluding by dancing the Bergamask Dance. The clock strikes midnight: the hour of the fairies is at hand. Theseus sends the wedding party to bed.
Puck and the fairies, followed by Oberon and Titiana, enter the palace to cleanse the place of harmful spirits and bless it. “If we shadows have offended, Think but this, and all is mended, That you have but slumber'd here, While these visions did appear. And this weak and idle theme, No more yielding but a dream...”