Leporello is standing guard while his master Don Giovanni is enjoying another adventure. This time, he is trying to seduce Donna Anna. Anna’s father, the Commendatore, arrives and challenges him to a duel. Don Giovanni kills the Commendatore and escapes unidentified. Donna Anna makes her fiancé, Don Ottavio, swear that he will avenge her father’s death.
Don Giovanni meets Donna Elvira, to whom he has once professed his love (Elvira: Ah! chi mi dice mai quel barbaro dov’è). Leporello tells Elvira about Don Giovanni’s innumerable conquests in his catalogue aria (Madamina, il catalogo è questo). Elvira has been just one of Don Giovanni’s 2065 conquests.
Zerlina and Masetto are celebrating their wedding. Attracted to the bride, Don Giovanni invites the entire wedding party to his home. Meanwhile, Leporello is tasked with keeping away the groom, Masetto. Don Giovanni tries to have his way with Zerlina (duet Là ci darem la mano), but Donna Elvira interferes. When Donna Anna and Don Ottavio arrive, Anna recognises her father’s murderer and demands revenge (Or sai chi l’onore).
At the party, Don Giovanni sings a drinking song (Fin ch’han dal vino) and attempts to seduce Zerlina again while everyone is dancing. When Donna Anna accuses him of murder, Don Giovanni escapes, leaving Leporello unconscious amidst the revelry.
Leporello rebels – he no longer wants to serve his immoral master, but Don Giovanni bribes him to carry on. Now Don Giovanni is interested in Elvira’s maid and exchanges clothes with Leporello to seduce her. Leporello takes Elvira away, while Giovanni serenades the girl (Deh! vieni alla finestra).
Masetto arrives to wreak his revenge, and Leporello, mistaken for Don Giovanni, has to run away. He reveals his identity to the men, and manages to escape. Don Ottavio sings about his love for Anna (Il mio tesoro intanto).
Don Giovanni is approached by the corpse of the Commendatore whom he has killed. He invites the corpse to dinner, and the invitation is accepted.
With the dinner about to start, Donna Elvira implores Don Giovanni to change his ways, but her efforts are in vain. The corpse of the Commendatore makes an entrance as promised and demands that Don Giovanni take responsibility for his actions. Don Giovanni refuses to repent.