Tybalt fatally wounds Mercutio in Shakespeare’s Romeo and Juliet. The injury occurs during the street confrontation between Tybalt and Romeo, with Mercutio intervening.
Romeo initially refuses to fight Tybalt because Tybalt has become his relative by marriage after Romeo secretly marries Juliet. Mercutio does not know about that marriage and is angered by Romeo’s reluctance. When Mercutio and Tybalt fight, Romeo tries to separate them, and Tybalt strikes Mercutio under Romeo’s arm.
Mercutio’s famous response, “A plague o’ both your houses!”, condemns both families before he dies. His death changes the play’s direction: Romeo kills Tybalt in revenge, and Prince Escalus banishes Romeo from Verona.
A frequent mistake is to say Romeo kills Mercutio. Romeo contributes to the fatal moment by intervening, but Tybalt delivers the wound that kills Mercutio.