A chorus introduces the story of the endless feud between the Montague and Capulet families, and of the love between their children, Roméo and Juliette.

ACT I

Verona, 14th century.

At a masked ball at the Capulet palace, Tybalt waits for his cousin Juliette and assures her suitor, Count Paris, that her beauty will overwhelm him. Capulet presents his daughter to the guests and invites them to dance. The crowd disperses and Roméo, a Montague, enters with his friends Mercutio and Benvolio. He tells them about a strange dream he has had, but Mercutio dismisses it as the work of the fairy Queen Mab ('Mab, reine des mensonges'). Roméo watches Juliette dance and is instantly entranced with her. Juliette tells her nurse that she is not interested in marriage ('Je veux vivre'), but when Roméo approaches her, both feel that they are meant for each other. Just as they discover each other’s identity, Tybalt returns. Roméo masks himself and rushes off. Tybalt identifies the intruder as Montague's son, but Capulet restrains him, ordering the party to continue.