Leporello stands guard as he waits for his master, Don Giovanni, and complains about his life as a servant (Notte e giorno faticar). He is the lookout as Don Giovanni sneaks into the Commendatore’s house to attempt to seduce his daughter, Donna Anna, in disguise. Don Giovanni enters, being followed by Donna Anna, who insists that he unmask himself, and eventually screams for help. The Commendatore enters and forces Giovanni into a duel, for the honor of his daughter. Don Giovanni kills him and flees with Leporello. Donna Anna, having run for help, returns with her fiancée, Don Ottavio, only to find her father murdered. Devastated, she demands that Don Ottavio find vengeance against the man and bring him to justice (Ma qual mai s’offre).
In a square in Seville, Giovanni and Leporello come across a woman who is declaring her revenge about being betrayed by a former lover. Giovanni attempts to flirt with her, only to discover that she is Donna Elvira, his former lover, and she is seeking revenge for his actions. Don Giovanni flees, and Leporello tells her that he is not worth her tears, stating how many lovers he has conquested in each city (Madamina!). At that moment, a procession enters the square in honor of Masetto and Zerlina’s wedding (Giovinette, che fate all’amore). Don Giovanni returns and finds Zerlina incredibly attractive, therefore offering to host a wedding celebration at this castle. Masetto attempts to leave with his bride, but Don Giovanni sends him away so he can be alone with Zerlina (Ho capito). Don Giovanni seduces Zerlina and starts to bring her back to his castle when Donna Elvira interrupts and takes erlina away from Don Giovanni (Là ci darem la mano...Ah! fuggi il traditor). Don Ottavio and Donna Anna enter, in the midst of plotting to find the murderer.
Upon seeing Don Giovanni, a very respected man in society, Donna Anna asks him for his help, not knowing that he is, in fact, her seducer. Giovanni is relieved that she does not