ACT I
A wood near Athens
A gathering of fairies, attendants of Tytania, Queen of the Fairies, is interrupted by Puck, the servant of Oberon, King of the Fairies. Tytania and Oberon have quarrelled because she refuses to give him one of her attendants, an Indian boy, to be his page. Because of the quarrel, they have neglected their duties, and nature is in disarray. Determining on revenge, Oberon orders Puck to fetch him a magic herb, whose juice, dropped on a sleeper's eyelids, causes him to fall madly in love with the first creature he sees on waking. Oberon intends to use this on Tytania.
Lysander and Hermia are fleeing from the Athenian law which insists that Hermia obey her father and marry Demetrius, but they have been followed by Demetrius, who is in love with Hermia. He in turn is followed by Helena, who loves him so much that she has betrayed her friend Hermia's plans to him. Observed by Oberon, Demetrius spurns Helena and runs off. When Puck brings back the magic herb, Oberon tells him to anoint the eyes of an Athenian youth - Demetrius - to make him return Helena's love.
A group of Athenian tradesmen come to the wood to rehearse a play about Pyramus and Thisbe, which they hope to perform for the wedding of Theseus, the Duke of Athens, and Hippolyta, the Amazon Queen. The parts are assigned by Peter Quince, though not without some difficulty, as Nick Bottom wants to play every part, in addition to his proper role of Pyramus. They separate to learn their lines, agreeing to return to the spot for a rehearsal.
Lysander and Hermia reappear, exhausted from their wanderings, and lie down to sleep. Puck, mistaking Lysander for the Athenian youth mentioned by Oberon, puts the juice of the flower into his eyes. Demetrius runs through, pursued by Helena, who is too exhausted to follow him further. Seeing Lysander, she fears he may be dead, and wakes him up. Under the influence of the magic flower he falls madly in love with her, but she thinks he is mocking her and runs away. He follows her, abandoning Hermia, who wakes up to find herself alone. She sets off in search of Lysander.
Surrounded by her attendants, Tytania falls asleep, but Oberon creeps up and anoints her eyes with the magic juice, bidding her to "wake when some vile thing is near."
ACT II
The tradesmen start their rehearsal. Puck slips up behind Bottom and puts an ass' head on him. This frightens the others, who run away. Bottom is singing to himself to keep up his spirits, when Tytania wakes up and falls in love with him. She orders fairies to attend to his every wish. He is tired and goes to sleep.
Hermia meets Demetrius and accuses him of having killed Lysander. She continues her search and he lies down to sleep. Oberon, who is watching and has realised Puck's error, sends him to bring Helena to the spot so that she will be on hand when Demerius wakes, and puts the juice in Demetrius' eyes.
But when Helena appears, she is accompanied by Lysander,who is still protesting his devotion. When Demetrius wakes up and also expresses his sudden love, she is unable to believe that he is genuine. Hermia comes on the scene, to find that both men now love Helena, who accuses Hermia of having conspired with them to deride her. The two girls quarrel and Lysander and Demetrius prepare to fight over Helena. Angry at Puck's mistake, Oberon orders him to create a mist and lead the men astray so they cannot harm one another and then put them to sleep and anoint Lysander's eyes with an antidote. When this has been done, Puck brings the girls and puts them to sleep too.
ACT III
Tytania has given the Indian boy to Oberon, who now takes pity on her and undoes the spell. She is horrified to see the creature she has been in love with. Oberon orders Puck to remove the ass' head and Oberon and Tytania are reconciled.
The four young people wake up, paired off properly, wondering about what they have experienced.
Bottom wakes up to find himself again, but he has a strange intimation that something wonderful has happened to him. He is reunited with his friends and they learn that their play has been chosen. Theseus and Hippolyta are preparing for their marriage. The two pairs of lovers explain that their differences have been resolved and Theseus agrees that Hermia can marry the man of her choice. The "tedious brief scene" of Pyramus and Thisbe is performed and the three couples retire to bed. The fairies invoke a blessing on the palace and its occupants.