An old feud between the lords of two prominent Verona families, Capulet and Montague, flares up on the street outside of the Capulets' house and causes a fight among the servants and members of their households. The prince of Verona, who has the legal authority to rule in the city, threatens death if the violence continues.
Lord Montague's son, Romeo, enters after the street fight. He is in love with Rosaline, who does not love him back, so despair consumes him. His friends try to tease him out of his melancholy, but Romeo cannot be consoled.
Meanwhile, a young count named Paris has asked to marry Lord Capulet's 13-year-old daughter, Juliet. Lord Capulet gives Paris permission to woo Juliet that very night at a masquerade ball he's throwing. When Juliet's mother delivers this news, Juliet responds unenthusiastically that she will try to return Paris's interest.
Romeo learns that Rosaline will attend the Capulets' festival, so he and his friends sneak in. Romeo sees Juliet at the party and is so struck by her beauty that he forgets about Rosaline. He approaches Juliet, they flirt, and they fall headlong in love. Even though they discover their families are enemies and their relationship would be forbidden, they decide to get married the next day. Romeo goes to arrange it with Friar Lawrence.
Initially Friar Lawrence is dismayed at how quickly Romeo has transferred his love from Rosaline to Juliet, but the friar agrees to marry them in the hope that their union might resolve the feud between their families. That afternoon he weds the young lovers.
The tension between the feuding households simmers. Juliet's cousin Tybalt, offended by Romeo's uninvited presence at the party, challenges him to a fight. Romeo tries to avoid conflict with his wife's (and now his own) cousin. Then Romeo's best friend, the fiery Mercutio, insists on a duel to defend his friend's honor. Although Romeo tries to intervene, Tybalt kills Mercutio. Distraught, Romeo kills Tybalt and runs away. The prince arrives and announces that Romeo is banished from Verona under threat of death.
When Juliet finds out what has happened, she mourns for her dead cousin but is grateful her husband is alive. His banishment, however, seems worse than his death. When Juliet threatens to kill herself, the nurse promises to arrange for Romeo to come spend his wedding night with Juliet. The nurse finds Romeo at Friar Lawrence's cell, where the three conspire to sneak him into Juliet's room.
The next morning, after a sorrowful farewell, Romeo leaves for Mantua, intending to be reunited with Juliet once the friar has revealed their marriage to their parents and persuaded the prince to let him return. However, when Juliet's father decides (in ignorance of these events) that she will marry Paris that week, the friar's plan begins to unravel. When Juliet refuses to marry Paris, her father issues an ultimatum: do as he says, or he'll drive her out of the family. Desperate, Juliet runs to the friar for advice. He devises a plan in which Juliet will drink a potion that will make her appear dead. Then he will lay her body in the Capulet family crypt, where Romeo will meet her. The young newlyweds will then flee to Mantua until the Friar can make peace with their parents and the prince. When Juliet agrees, the friar plans to send a messenger to tell Romeo of the plan.
Juliet returns home and fakes obedience to her father, who moves the wedding date up a day to celebrate. Alone in her chamber, Juliet takes the potion. The next morning, when the nurse is sent to wake her for her wedding, she discovers Juliet "dead." The nurse, her parents, and Paris mourn. The friar arrives and directs them to begin the appropriate rituals and bring her body to the crypt.
Romeo does not receive the friar's letter. Instead, his servant Balthasar arrives and tells him that Juliet is dead. Heartbroken, Romeo secures poison from an apothecary, obtains materials to write his father an explanatory letter, and returns to Verona.
Outside of Juliet's crypt, Paris arrives to say farewell to her, instructing his page not to interrupt him unless someone approaches. As Paris strews flowers, Romeo appears. Paris seeks to detain Romeo, Tybalt's murderer, until the law arrives. Romeo tries to persuade Paris to leave him alone, but Paris will not, and both draw swords. Romeo kills Paris and then breaks into the crypt.
He finds Juliet there, as beautiful as ever. He embraces and kisses her and then drinks his poison and dies. Meanwhile, the friar has arrived and discovered from Balthasar that Romeo is within. As he approaches, he sees blood and weapons in the yard and hurries into the crypt. There he finds the bodies of Paris and Romeo. When Juliet awakens, he must show her Romeo's dead body. They hear a noise, and Friar Lawrence flees, begging Juliet to go with him, but she refuses. She kisses Romeo's lips in the hope that enough poison lingers there to kill her too. Then she takes Romeo's dagger and stabs herself to death.
Once the prince and all the family members gather at the crypt, Friar Lawrence tells what he knows. Romeo's letter to his father (whose wife has just died upon hearing of Romeo's banishment) fills in the rest. Moved by the young people's faithful love, Montague takes Capulet's hand and says he will build a golden statue of Juliet. Capulet says he will do the same for Romeo. In this way the feud between the families ends.