In a court in Athens, Duke Theseus prepares for his marriage to Hippolyta, Queen of the Amazons. He is interrupted by a courtier, Egeus. Egeus asks for Theseus to intervene in a dispute. His daughter, Hermia, will not agree to marry Demetrius (whom Egeus has chosen for her) because she loves a gentleman named Lysander. Duke Theseus asks Hermia to be obedient to Egeus, her father. He offers her one of two options: Hermia must either die or marry Demetrius.
Naturally upset with the offer, Lysander and Hermia plan to run away to the Forest and elope; they share their secret with Helena, Hermia's friend. Helena is desperately in love with Demetrius, who seems to have abandoned her in favour of Hermia. At night, Lysander and Hermia escape from Athens; but they soon lose their way in the Forest. After Helena tells him of their intention to defy the law, Demetrius decides to follow the lovers into the Forest. In turn, Helena follows Demetrius into the forest with the hope that he will give up on Hermia and choose her instead.
Meanwhile in Athens, a group of handymen, called the Rude Mechanicals are preparing a play of the tragic love-story of Pyramus and Thisbe to present before Duke Theseus on his wedding day. Peter Quince, the director, casts the play: Nick Bottom, the weaver, is to play the lover Pyramus, while Francis Flute, the bellows-mender, begrudgingly agrees to play Thisbe. Snout, Snug, and Starveling fill out the world and they make plans to rehearse in the Forest.
Nearby in the Forest, Oberon - King of the Fairies—has recently quarreled with his queen, Titania. She acquired a magical child from one of her waiting women, and Oberon wants the child as a page, but Titania refuses. Oberon begins to plot a way to get revenge on Titania for not following his wishes. He sends his fairy servant, Puck, to fetch a purple flower with juice that makes people fall in love with the next creature they see.
Afterwards, Oberon overhears Helena and Demetrius arguing in the forest. Oberon hears Demetrius mistreat Helena and tells Puck to anoint 'the Athenian', so Demetrius will fall in love with the first person that he sees. Puck mistakes the Athenian and puts the flower juice on the eyes of the sleeping Lysander. When he is woken by Helena, he immediately falls in love with her and rejects Hermia. When Demetrius rests, Oberon puts magic juice on his eyes, which makes him fall in love with Helena as well.
Quince, Snug, Snout, Starveling, Flute, and Bottom rehearse in the Forest until overheard by Puck, who plays a trick on them by giving Bottom an ass's head. After frightening the Mechanicals away, Bottom is lured towards the sleeping Titania whom Oberon has anointed with magic flower juice. On waking, the Titania falls in love with Bottom and entertains him with her fairies: Peaseblossom, Cobweb, Moth, and Mustardseed
Demetrius and Lysander, still under the spell of the flower juice, pursue Helena. Hermia is jealous and confused about Lysander’s change in heart, and blames Helena. Oberon and Puck watch the chaos, and Oberon commands Puck to put it right again. The lovers' arguments have tired them all out as they have chased one another through the woods. Puck eventually distracts Demetrius and Lysander from their pursuit of Helena by impersonating their voices, and they get lost in the woods. The Lovers fall asleep, exhausted. Puck places restorative juice on Lysander's eyes.
After an afternoon of being pampered by The Fairies, Bottom and Titania fall asleep. Oberon restores Titania's sight and wakes her (having stolen the boy from her). After expressing her dismay at the sight of Bottom, Titania reconciles with her king. Bottom's ass head is removed, and he returns to Athens to rejoin The Mechanicals as they prepare to perform their play. The lovers are woken by Theseus and Hippolyta's hunting party. Lysander and Hermia reconcile, and Demetrius professes his rekindled love for Helena.
Happily reunited and returned to Athens, The Lovers agree to share the Duke's wedding day. The Mechanicals’ play of 'Pyramus and Thisbe' is presented before Theseus, Hippolyta, and The Lovers. As the three couples retire to bed, Puck and the Fairies return to bless the palace and its people.