The play features three interlocking plots, connected by a celebration of the wedding of Duke Theseus of Athens and the Amazon queen, Hippolyta, and set simultaneously in the woodland, and in the realm of Fairyland, under the light of the moon.
In the opening scene, Hermia refuses to follow her father Egeus's instructions to marry Demetrius, whom he has chosen for her. In response, Egeus quotes before Theseus an ancient Athenian law whereby a daughter must marry the suitor chosen by her father, or else face death. Theseus offers her another choice: lifelong chastity worshiping the goddess Diana as a nun.
At that same time, Quince and his fellow players were engaged to produce an act which is "the most lamentable comedy and most cruel death of Pyramus and Thisbe", for the Duke and the Duchess. Peter Quince reads the names of characters and bestows them to the players. Nick Bottom who is playing the main role of Pyramus, is over-enthusiastic and wants to dominate others by suggesting himself for the characters of Thisbe, The Lion and Pyramus at the same time. Also he would rather be a tyrant and recites some lines of Ercles or Hercules. Quince ends the meeting with "at the Duke's oak we meet".
Meanwhile, Oberon, king of the fairies, and his queen, Titania, have come to the forest outside Athens. Titania tells Oberon that she plans to stay there until after she has attended Theseus and Hippolyta's wedding. Oberon and Titania are estranged because Titania refuses to give her Indian changeling to Oberon for use as his "knight" or "henchman," since the child's mother was one of Titania's worshipers. Oberon seeks to punish Titania's disobedience, so he calls for his mischievous court jester Puck or "Robin Goodfellow" to help him apply a magical juice from a flower called "love-in-idleness," which when applied to a person's eyelids while sleeping makes the victim fall in love with the first living thing seen upon awakening. He instructs Puck to retrieve the flower so that he can make Titania fall in love with the first thing she sees when waking from sleep, which he is sure will be an animal of the forest. Oberon's intent is to shame Titania into giving up the little Indian boy. He says, "And ere I take this charm from off her sight, / As I can take it with another herb, / I'll make her render up her page to me."
Having seen Demetrius act cruelly toward Helena, Oberon orders Puck to spread some of the magical juice from the flower on the eyelids of the young Athenian man. Instead, Puck mistakes Lysander for Demetrius, not having actually seen either before. Helena, coming across him, wakes him while attempting to determine whether he is dead or asleep. Upon this happening, Lysander immediately falls in love with Helena. Oberon sees Demetrius still following Hermia and is enraged. When Demetrius decides to go to sleep, Oberon sends Puck to get Helena while he charms Demetrius' eyes. Upon waking up, he sees Helena. Now, both men are in pursuit of Helena. However, she is convinced that her two suitors are mocking her, as neither loved her originally. Hermia is at a loss to see why her lover has abandoned her, and accuses Helena of stealing Lysander away from her. The four quarrel with each other until Lysander and Demetrius become so enraged that they seek a place to duel each other to prove whose love for Helena is the greatest. Oberon orders Puck to keep Lysander and Demetrius from catching up with one another and to remove the charm from Lysander, so that he goes back to being in love with Hermia.
Meanwhile, a band of six labourers ("rude mechanicals", as they are described by Puck) have arranged to perform a play about Pyramus and Thisbe for Theseus' wedding and venture into the forest, near Titania's bower, for their rehearsal. Nick Bottom, a stage-struck weaver, is spotted by Puck, who (taking his name to be another word for a jackass) transforms his head into that of a donkey. When Bottom returns for his next lines, the other workmen run screaming in terror. Determined to wait for his friends, he begins to sing to himself. Titania is awakened by Bottom's singing and immediately falls in love with him. She lavishes him with attention, and presumably makes love to him. While she is in this state of devotion, Oberon takes the changeling. Having achieved his goals, Oberon releases Titania, orders Puck to remove the donkey's head from Bottom, and arrange everything so that Hermia, Lysander, Demetrius, and Helena will believe that they have been dreaming when they awaken. The magical enchantment is removed from Lysander, leaving Demetrius under the spell and in love with Helena.
The fairies then disappear, and Theseus and Hippolyta arrive on the scene, during an early morning hunt. They wake the lovers and, since Demetrius does not love Hermia any more, Theseus overrules Egeus's demands and arranges a group wedding. The lovers decide that the night's events must have been a dream. After they all exit, Bottom awakes, and he too decides that he must have experienced a dream "past the wit of man". In Athens, Theseus, Hippolyta and the lovers watch the six workmen perform Pyramus and Thisbe. The play is badly performed to the point where the guests laugh as if it were meant to be a comedy, and afterward everyone retires to bed. Afterward, Oberon, Titania, Puck, and other fairies enter, and bless the house and its occupants with good fortune. After all other characters leave, Puck "restores amends" and reminds the audience that this might be nothing but a dream (hence the name of the play).