The murder of Gonzago was performed in what Shakespeare play?

The House of Gonzaga is the inspiration for the play-within-the-play in Shakespeare's Hamlet. In Act 3 scene 2, they act out a play called The Murder of Gonzago (or The Mousetrap).

Hamlet tells the audience in act 2, scene 2 that he will have the players, who arrive at Elsinore in this scene, "Play something like the murder of my father / Before mine uncle." He intends, in other words, to put on a play that reenacts the circumstances of his father's murder (as described by the Ghost).

He will then watch Claudius and judge from his reaction whether he is actually guilty of the murder before pursuing revenge. The Murder of Gonzago is the name of the play in question, intended to, as Hamlet says, "catch the conscience of the King."