Leporello, Don Giovanni's disgruntled servant, stands guard while his masked master pursues Donna Anna indoors. The Commendatore, Anna's father, challenges Giovanni to a duel, and the Don easily kills the old man. Anna emerges to find her father dead, and she and her fiancé Ottavio swear to avenge him.
Giovanni and Leporello see a mysterious beauty, who turns out to be Donna Elvira, already seduced and abandoned by the libertine. Giovanni makes his escape, and Leporello distracts her with a list of his master's conquests.
Giovanni's wandering eye settles next on the peasant girl Zerlina, so he tries to distract Zerlina's betrothed, Masetto. Just as the Don persuades Zerlina to join him, Elvira appears and convinces her to flee instead. Donna Anna and Don Ottavio enter, asking Giovanni to help find her father's murderer. He agrees, but after he leaves, Anna realizes that Giovanni was her masked assailant and Ottavio vows to avenge her.
With Leporello, Giovanni arranges a ball for Zerlina and Masetto. Masetto berates her for her flirtation with the Don. She attempts to mollify him, but once Giovanni returns, Zerlina's resolve grows weak. She is only able to resist because Masetto is near. Anna, Elvira and Ottavio enter, masked, and Leporello tells them to join the revelers, but a call for help from Zerlina interrupts the party. The maskers rush to rescue her. Giovanni insists that Leporello is guilty, but the three know better. They warn the Don that a storm of vengeance will soon rage around him.
Fed up, Leporello threatens to quit, so Giovanni bribes him to stay but he refuses to give up womanizing. Elvira's maid is the target of the day, and Giovanni switches clothes with Leporello and serenades the maid. Masetto arrives with a band of peasants hoping to kill Giovanni. Still disguised as Leporello, the Don tells the band to split up and takes Masetto aside. Once the others are out of earshot, Giovanni beats Masetto and leaves.
Meanwhile, Leporello, still wearing Giovanni's cloak and hat, has tired of Elvira's cooing and tries to get away from her. Anna, Ottavio, Masetto and Zerlina block his exit and, thinking they've caught Giovanni, agree to kill the reprobate. Leporello reveals himself, begs for mercy, and rushes away. Ottavio swears vengeance and Elvira expresses dismay over Giovanni's actions.
Leporello meets his master in the graveyard. As Giovanni boisterously describes his escapades, a voice interrupts and warns the scoundrel that his laughter will be silenced by morning. Leporello thinks in horror that perhaps they have heard the voice of the Commendatore. Giovanni laughs and orders his servant to invite the statue to dinner that evening.
Meanwhile, Ottavio tries to discuss marriage with Anna, but she says she cannot think of it in her sorrow.
Giovanni is about to sit down to dinner when Elvira storms in and begs him to return to her. Indifferent, Giovanni demands that she leave, but something terrifying interrupts her departure. She screams and runs out. Her fear is justified: the Commendatore has arrived, as invited. When Giovanni refuses to repent for his misdeeds, the Commendatore drags him to hell. The others rush in, and Leporello tells them what has happened. The libertine has received a just punishment.