Count Almaviva has fallen in love from afar with Rosina. He serenades her, hoping to win her heart. The Count hides when Figaro bursts in, boasting that he is the busiest man in the whole city. Figaro tells the Count that Rosina is kept a virtual prisoner, as the ward of the jealous Doctor Bartolo. The Count launches into another serenade, calling himself Lindoro, an impoverished student. Rosina’s attempt to communicate with “Lindoro” is thwarted and Figaro suggests that the Count disguise himself as a soldier, in order to gain entrance to the house.

Rosina resolves to reject Bartolo’s marriage proposal in favor of “‘Lindoro.” Don Basilio, Rosina’s music teacher, arrives to give a voice lesson. He warns Bartolo about the return of Count Almaviva and proposes a campaign of ever-increasing slander to drive him away. Figaro, having overheard them, alerts Rosina that the Doctor plans to marry her the next day. Almaviva arrives, disguised as a drunken soldier and demanding a night’s lodging. He argues loudly with Bartolo, meanwhile slipping a love note to Rosina. Figaro rushes in, followed by the police, whose attempt to arrest the “soldier” is thwarted.

Bartolo’s pleasure at getting rid of the soldier is interrupted by the arrival of “Don Alonzo,” who is substituting for the supposedly ailing Don Basilio. “Alonzo” is, of course, Count Almaviva in a new disguise. Rosina begins her lesson while Figaro shaves the Doctor. The hale and hearty Basilio appears, much to everyone’s surprise, but Almaviva bribes him to feign illness. Almaviva and Rosina plan to elope at midnight, but Bartolo overhears them; he sends Rosina to her room and throws Figaro and “Don Alonzo” out into the street.

Bartolo persuades Rosina that “Lindoro” is a servant of Almaviva, who is plotting her seduction. Rosina agrees to marry Bartolo. Figaro and Almaviva arrive during a violent thunderstorm and Rosina accuses them of betrayal. Almaviva finally reveals his true identity and is reconciled with Rosina. Bartolo returns too late and has no choice but to join in a chorus of rejoicing for the bride and groom.