Don Giovanni, a young, arrogant, and sexually promiscuous nobleman, abuses and outrages everyone else in the cast, until he encounters something he cannot kill, beat up, dodge, or outwit.
Leporello, Don Giovanni's servant, complains of his lot. He is keeping watch while Don Giovanni has entered the Commendatore's house in an attempt to seduce the Commendatore's daughter, Donna Anna. Don Giovanni enters the garden from inside the house, pursued by Donna Anna. Giovanni is masked and Donna Anna insists on knowing his true identity before he can break free from her grasp she cries for help. The Commendatore appears and forces Giovanni to fight a duel while Donna Anna flees to seek help. Giovanni kills the Commendatore with his sword and escapes with Leporello. Anna, returning with her fiancé, Don Ottavio, is horrified to see her father lying dead in a pool of his own blood. She makes Ottavio swear vengeance against the unknown murderer.
Scene 2 – A public square outside Don Giovanni's palace
Giovanni and Leporello arrive and hear a woman (Donna Elvira) singing of having been abandoned by her lover, on whom she is seeking revenge. Giovanni starts to flirt with her, but it turns out he is the former lover she is seeking. The two recognize each other and she reproaches him bitterly. He shoves Leporello forward, ordering him to tell Elvira the truth, and then hurries away.
Leporello tells Elvira that Don Giovanni is not worth her feelings for him. He is unfaithful to everyone; his conquests include 640 women and girls in Italy, 231 in Germany, 100 in France, 91 in Turkey, but in Spain, 1,003.
Scene 3 – The open country
A marriage procession with Masetto and Zerlina enters. Don Giovanni and Leporello arrive soon after. Giovanni is immediately attracted to Zerlina, and he attempts to remove the jealous Masetto by offering to host a wedding celebration at his castle. On realizing that Giovanni means to remain behind with Zerlina, Masetto becomes angry but is forced to leave. Don Giovanni and Zerlina are soon alone, and he immediately begins his seductive arts.
Elvira arrives and thwarts the seduction. She leaves with Zerlina. Ottavio and Anna enter, plotting vengeance on the still unknown murderer of Anna's father. Anna, unaware that she is speaking to her attacker, pleads for Giovanni's help. Giovanni, relieved that he is unrecognized, readily promises it, and asks who has disturbed her peace. Before she can answer, Elvira returns and tells Anna and Ottavio that Giovanni is a false-hearted seducer. Giovanni tries to convince Ottavio and Anna that Elvira is insane. As Giovanni leaves, Anna suddenly recognizes him as her father's murderer and tells Ottavio the story of his intrusion, claiming that she was deceived at first because she was expecting a night visit from Ottavio himself, but managed to fight Giovanni off after discovering the imposture, leading to the events we have already witnessed. Ottavio, not yet convinced (Anna having only recognized Giovanni's voice, not seen his face), resolves to keep an eye on his friend.
Leporello informs Giovanni that all the guests of the peasant wedding are in Giovanni's house and that he distracted Masetto from his jealousy, but that Zerlina, returning with Elvira, made a scene and spoiled everything. However, Don Giovanni remains cheerful and tells Leporello to organize a party and invite every girl he can find.
Scene 4 – A garden outside Don Giovanni's palace
Zerlina follows the jealous Masetto and tries to pacify him, but just as she manages to persuade him of her innocence, Don Giovanni's voice from offstage startles and frightens her. Masetto hides, resolving to see for himself what Zerlina will do when Giovanni arrives. Zerlina tries to hide from Don Giovanni, but he finds her and attempts to continue the seduction, until he stumbles upon Masetto's hiding place. Confused but quickly recovering, Giovanni reproaches Masetto for leaving Zerlina alone, and returns her temporarily to him. Giovanni then leads both offstage to his ballroom. Three masked guests – the disguised Ottavio, Anna, and Elvira – enter the garden. From a balcony, Leporello invites them to his master's party. They accept the invitation and Leporello leaves the balcony. Alone, Ottavio and Anna pray for protection, Elvira for vengeance.
Scene 5 – Don Giovanni's ballroom
As the merriment, featuring three separate chamber orchestras on stage, proceeds, Leporello distracts Masetto by dancing with him, while Don Giovanni leads Zerlina offstage to a private room. When Zerlina screams for help, Don Giovanni tries to fool the onlookers by dragging Leporello into the room and threatening to kill him for assaulting Zerlina. But Ottavio produces a pistol, and the three guests unmask and declare that they know all. But despite being denounced on all sides, Don Giovanni escapes – for the moment.
Scene 1 – Outside Elvira's house
Leporello threatens to leave Giovanni, but his master calms him with a peace offering of money. Wanting to seduce Elvira's maid and believing that she will trust him better if he appears in lower-class clothes, Giovanni persuades Leporello to exchange cloak and hat with him. Elvira comes to her window. Seeing an opportunity for a game, Giovanni hides and sends Leporello out in the open wearing Giovanni's cloak and hat. From his hiding place Giovanni sings a promise of repentance, expressing a desire to return to her and threatening to kill himself if she does not take him back, while Leporello poses as Giovanni and tries to keep from laughing. Elvira is convinced and descends to the street. Leporello, continuing to pose as Giovanni, leads her away to keep her occupied while Giovanni serenades her maid with his mandolin.
Before Giovanni can complete his seduction of the maid, Masetto and his friends arrive, searching for Giovanni with the intent of killing him. Giovanni (still disguised as Leporello) convinces the posse that he also hates Giovanni and joins the hunt. After cunningly dispersing Masetto's friends (Giovanni aria: "Metà di voi qua vadano" – "Half of you go this way,") Giovanni takes Masetto's weapons away, beats him up, and runs off, laughing. Zerlina arrives and consoles the bruised and battered Masetto ("Vedrai carino" – "You'll see, dear one").
Scene 2 – A dark courtyard
Leporello abandons Elvira. As he tries to escape, Ottavio arrives with Anna, consoling her in her grief. Just as Leporello is about to slip through the door, which he has difficulty finding, Zerlina and Masetto open it and, seeing him dressed as Giovanni, catch him before he can escape. When Anna and Ottavio notice what is going on, all move to surround Leporello, threatening him with death. Elvira tries to protect the man who she thinks is Giovanni, claiming that he is her husband and begging for pity. The other four resolve to punish the traitor, but Leporello removes his cloak to reveal his true identity. He begs for mercy and, seeing an opportunity, runs off. Given the circumstances, Ottavio is now convinced that Giovanni was the murderer of Donna Anna's father (the deceased Commendatore) and swears vengeance. Elvira is still furious at Giovanni for betraying her, but she also feels sorry for him.
Scene 3 – A graveyard with the statue of the Commendatore.
Leporello tells Don Giovanni of his brush with danger, and Giovanni taunts him, saying that he took advantage of his disguise as Leporello by trying to seduce one of Leporello's girlfriends. But the servant is not amused, suggesting it could have been his wife, and Don Giovanni laughs aloud at his servant's protests. The voice of the statue warns Giovanni that his laughter will not last beyond sunrise. At the command of his master, Leporello reads the inscription upon the statue's base: "Here am I waiting for revenge against the scoundrel who killed me". The servant trembles, but the unabashed Giovanni orders him to invite the statue to dinner, threatening to kill him if he does not. Leporello makes several attempts to invite the statue to dinner but for fear cannot complete the task. It falls upon Don Giovanni himself to complete the invitation, thereby sealing his own doom. Much to his surprise, the statue nods its head and responds affirmatively.
Scene 4 – Donna Anna's room
Ottavio pressures Anna to marry him, but she thinks it inappropriate so soon after her father's death. He accuses her of being cruel, and she assures him that she loves him, and is faithful.
Scene 5 – Don Giovanni's chambers
Giovanni revels in the luxury of a great meal, served by Leporello, and musical entertainment during which the orchestra plays then-contemporary late-18th-century operatic music: "O quanto in sì bel giubilo" from Vicente Martín y Soler's Una cosa rara (1786), "Come un agnello" from Giuseppe Sarti's Fra i due litiganti il terzo gode (1782) and finally, "Non più andrai" from Mozart's own The Marriage of Figaro (1786). Elvira appears, saying that she no longer feels resentment for Giovanni, only pity. Surprised by her lack of hatred, Giovanni asks what it is that she wants, and she begs him to change his life. Giovanni taunts her and then turns away, praising wine and women as the "support and glory of humankind". Hurt and angry, Elvira gives up and leaves. A moment later, her scream is heard from outside the walls of the palace, and she returns only to flee through another door. Giovanni orders Leporello to see what has upset her; upon peering outside, the servant also cries out, and runs back into the room, stammering that the statue has appeared as promised. An ominous knocking sounds at the door. Leporello, paralyzed by fear, cannot answer it, so Giovanni opens it himself, revealing the statue of the Commendatore. With the D minor cadences from the overture now accompanying the bass voice, the Commendatore offers a last chance to repent, but Giovanni adamantly refuses. The statue disappears and Don Giovanni cries out in pain and terror as he is surrounded by a chorus of demons, who carry him down to Hell. Leporello, watching from under the table, also cries out in fear.
Donna Anna, Don Ottavio, Donna Elvira, Zerlina, and Masetto arrive, searching for the villain. They find instead Leporello hiding under the table, shaken by the supernatural horror he has witnessed. Giovanni is dead. Anna and Ottavio will marry when Anna's year of mourning is over; Elvira will spend the rest of her life in a convent; Zerlina and Masetto will finally go home for dinner; and Leporello will go to the tavern to find a better master.
The concluding ensemble delivers the moral of the opera – "Such is the end of the evildoer: the death of a sinner always reflects his life."