Figaro, valet to Count Almaviva, and Susanna, maid to the Countess, are discussing their forthcoming marriage while they measure a room which has been assigned to them for use after the event. Meanwhile, Marcellina and Dr. Bartolo are hatching a blackmail plot in which Marcellina would win Figaro, who owes her money, as her husband. Cherubino, who loves the Countess, comes to Susanna to ask her intervention with the Countess to help him be re-instated as the Count’s page. In the midst of this, the Count arrives and Cherubino is forced to hide. The Count begins advances to Susanna, is interrupted by Don Basilio, and hides behind a chair. However, he is enraged by Basilio’s conversation and re-appears, much to Basilio’s delight. The Count then relates a story of finding Cherubino in Barbarina’s rooms and, in the course of this storytelling, uncovers Cherubino, who has been hiding in the chair. The Count, in a dreadful state, banishes Cherubino to a far-off regiment and Figaro and Susanna tease the elegant Cherubino about his coming life in the army.

Figaro and Susanna explain to the Countess what has happened. They plan for Cherubino, dressed as Susanna, to meet secretly with the Count and hand him a note stating that the Countess has made a rendezvous with an unknown man. Cherubino enters to try on his dress but no sooner is he buttoned in than the Count knocks at the locked door. Cherubino dashes into a closet, locking the door, and Susanna hides behind a screen. The Count of course is distrustful. When he and the Countess leave for a moment Cherubino jumps out of the window and Susanna replaces him in the closet. The first two return and discover Susanna. In the midst of much excitement and many accusations Marcellina enters to complain of Figaro’s breach of promise to her.

Susanna and the Count agree to meet at midnight in the garden. Susanna assures Figaro he should not worry about Marcellina and her breach of promise threat. The Count overhears this advice and is furious. He at once declares Marcellina to be in the right but soon changes his attitude when it is learned that she is really Figaro’s long-lost mother, Figaro being the flower of Marcellina’s earlier dalliance with Dr. Bartolo. During the marriage of Figaro and Susanna, Susanna slips a note to the Count which she and the Countess had written earlier in the day.

Unaware that the Countess and Susanna have exchanged dresses, Figaro is angered to find the Count in a tête-a- tête with “Susanna” but Figaro, as he sees through the disguise, begins making love to the “Countess”. The “Countess” and Figaro pretend to the Count that they are in love. He, wild with jealousy, calls for all within the castle walls to witness this scandalous behavior. At the height of his rage “Susanna” reveals herself as the Countess, the Count begs forgiveness and the opera ends with great rejoicing.