The Count's man-servant Figaro is delighted when he learns that the Count would like to present him and his fiancee Susanna, chamber-maid for the Countess, with a bed as a wedding gift. The Count even promised the use of a room in his castle. Susanna confesses Figaro her worries about the Count who has been trying to seduce her for some time now. She points out that that particular room is located very closely to the Count's bed-room; it will therefore enable the Count to pursue her with even more ease. As a result, Figaro declares war on the Count. Marcellina who works as house-keeper for Dr. Bartolo wants to force Figaro to marry her instead of Susanna: he is indebted to her as he once promised Marcellina to marry her in return for a financial loan. Bartolo who has long been Figaro's enemy promises Marcellina his help in that matter. The page Cherubino bursts into Susanna's room. He begs her to plead with the Count on his behalf: he decided to drive Cherubino out of the castle after he discovered him in a tête-à-tête with the young girl Barbarina. When the Count enters the room, Cherubino hides himself. The Count offers Susanna money for the exchange of one night with her. Suddenly Basilio, the Count's “factotum” enters the room and the Count is forced to hide as well. Basilio accuses Susanna and the Countess of flirting with Cherubino. Provoked by these accusations the outraged Count leaves his hiding place and as a result the anxious Susanna looses her consciousness. The Count discovers Cherubino, but his anger is interrupted by Figaro who enters the room and asks the Count to follow him into an adjacent room: some of the farm workers await the Count's official opening of the wedding ceremonies. To everybody's annoyance, however, the Count decides to postpone the wedding. Under the pretence of his amorous adventures being pardoned, Cherubino is sent to war by the Count.
Meanwhile, the Countess has sunk into a depression, because she has lost her husband's love. When Susanna enters the room, the Countess interrogates her about the Count's advances. Soon Figaro appears and lets them in on his scheme against the Count who should be informed about a rendez-vous between the Countess and a presumed lover: the ensuing jealousy should be enough to distract the Count from Susanna. Furthermore, Susanna ought to ask him for a rendez-vous in the garden, where Cherubino – dressed as a girl – will turn up and therefore expose the Count. Susanna and the Countess agree to the plan. They dress Cherubino. When the Count suddenly appears, the Countess quickly hides Cherubino in her cabinet. She then refuses to open its door. Beside himself with rage, the Count storms out of the room with the Countess to fetch the necessary tools and to break open the cabinet door. It is at that moment that Cherubino jumps out of the window and that Susanna slips into his hiding-place instead. Fearing the Count's brutality, the Countess finally confesses and names the person hiding in the cabinet; she then pleads for mercy on Cherubino's behalf. But after all that, it is Susanna who suddenly steps out of her hiding-place and the mortified Count has to ask forgiveness from his wife. Figaro's second attempt in convincing the Count to open the wedding ceremonies is interrupted by the gardener: the man complains about people jumping out of the window and straight into his flower bed. To save the situation Figaro steps forward and names himself as the one who did it. Bartolo and Marcellina join the group. They demand that Figaro marry Marcellina as so far he had not been able to pay his debts. A date for a clarifying trial is set.
With the Countess' approval Susanna promises the Count a rendez-vous in the garden. The Countess will then meet her husband in Susanna's clothes. When Figaro whispers in Susanna's ears that the court trial has most likely already been decided in his favour, the Count again becomes suspicious: he swears to interfere with Figaro's wedding plans. Marcellina's interest ought to help him in that. In the meantime, Cherubino dresses up as a girl with Barbarina's help; that way it will be easier for him to hide himself in the castle. The Countess waits for news from Susanna and then decides to take the course of her life into her own hands. During the trial Bartolo and Marcellina suddenly recognize Figaro as their son which lets the Count's plans come to a sudden stand-still. Susanna wants to pay Figaro's debts and appears on the scene only to find Figaro in Marcellina's arms. The misunderstanding, however, is quickly solved. With Susanna’s help the Countess writes a second letter to the Count, in which she asks him again for a rendez-vous. A group of young women with the disguised Cherubino amongst them have decided to present the Countess with flowers. During that moment Cherubino is recognized. Barbarina resolves the difficult situation by asking for Cherubino's hand in marriage. With everybody present the two cou-ples – Figaro and Susanna as well as Marcellina and Bartolo – finally get married. Whilst everybody celebrates, the Count discovers the letter in which he is asked for the rendez-vous in the garden.
Barbarina informs Figaro about the meeting. He departs angrily, despite Marcellina's pleadings: she does not believe in Susanna's unfaithfulness. Marcellina laments the fate of women and warns Susanna. Susanna then provokes Figaro by singing an aria about her longing for her lover. Figaro reacts with an angry litany about the female sex in general. Cherubino meanwhile is looking for Barbarina, but he happens to meet the Countess instead whom he mistakes for Susanna. He starts to make advances towards the Countess with the result that the observing Count moves in closer in order to hit Cherubino: in doing so, the Count unfortunately comes across the hovering Figaro. During the tête-à-tête with Susanna the confused Count does not recognize that it is really his wife he his holding in his arms. Figaro has recognized Susanna's voice and he decides to perform a love scene with Susanna, who is dressed in the Countess' clothes, for the sole benefit of the Count. The jealous Count calls out for witnesses. But when the real Countess steps forward, he recognizes his mistake and is pressed to openly acknowledge his guilt and unfaithfulness. The Count then asks his wife for her forgiveness.