At the beginning of the play, two of the young lovers, Hermia and Lysander, intend to flee together to the home of Lysander's aunt to put themselves out of the reach of Athenian law so they can get married. They agree to meet in the woods outside Athens and, from there, to journey to Lysander's aunt's home.
Lysander and Hermia confide their elopement plan to Helena. Helena is jealous of Lysander and Hermia and reveals the plan to Demetrius.
The next night, Lysander goes into the woods, where he meets with Hermia. Demetrius also goes into the woods, hoping to disrupt Lysander and Hermia's elopement plans, because he wants Hermia for himself. Helena follows Demetrius into the woods, hoping to rekindle his love for her.
In the meantime, Oberon, the king of the fairies, and his queen, Titania, are having an argument over a young Indian prince who was given to Titania. Oberon sends his servant, Puck, to find a magical flower.
Oberon puts the juice of the flower on Titania's eyes while she's sleeping. The juice acts as a love potion, which will make her fall madly in love with the first thing she sees when she wakes up.
Back in the forest, Lysander and Hermia are tired out from wandering around in the woods and lie down to sleep. Helena continues to chase Demetrius through the woods. Demetrius rejects her, and he runs off and leaves her alone.
Oberon sees how Demetrius is mistreating Helena, and he decides to teach Demetrius a lesson. Oberon has Puck go into the forest with the juice of the magical flower, with instructions to put the love potion on Demetrius's eyes, so that when he awakes, he'll fall in love with Helena.
Puck mistakenly puts the juice on Lysander's eyes, and when he wakes, the first person he sees is Helena. He instantly falls in love with her. Helena thinks that Lysander is mocking her and leaves him to go find Demetrius.
Lysander sees Hermia sleeping, realizes that he now hates her and wants nothing to do with her, and goes into the woods after Helena.
Hermia wakes up alone and goes looking for Lysander.
In the woods near where Titania is sleeping, a group of would-be actors is preparing a play to be presented at Theseus's wedding. Puck changes the head of Bottom, one of the actors, into an ass's head. The other actors are frightened by Bottom's new head, and they run away. Bottom thinks that they're playing a joke on him, and he starts singing to show the others that he's not afraid of being alone in the woods.
Bottom's singing wakes up Titania, who was sleeping nearby. Since Bottom is the first thing Titania sees when she awakens, she falls in love with him.
Oberon discovers that Puck has mistakenly put the love potion on Lysander's eyes, so he puts the love potion on the eyes of a sleeping Demetrius. Puck and Oberon stand aside as Lysander and Helena approach, arguing. Their arguing wakes up Demetrius, and the first person Demetrius sees is Helena.
Now Lysander and Demetrius are in love with Helena, Titania is in love with Bottom, and no one is in love with Hermia.
In time, of course, all of these mixed-up love matches are resolved. Lysander marries Hermia, Demetrius marries Helena, Titania is reunited with Oberon, and Bottom performs in the play for the Duke of Athens at the multiple wedding feast.