Figaro is in his new room, measuring for the bridal bed for him and Susanna after their wedding. Susanna comes in and tries on her wedding veil for him, and they enjoy each other as they plan for their upcoming wedding (Cinque, dieci, venti…). Figaro thinks that the room is perfect, but Susanna points out that it is too close to both of their masters, who will call them away in the middle of the night (Se a caso madam la notte ti chiama). Figaro brushes this off until Susanna reveals to him that the Count has been making advances on her, and she heard that he is going to use his feudal right before the wedding, allowing him to bed Susanna before her husband. The law was abolished when he married the Countess years ago, but he wants to reinstate it for Susanna. Figaro is enraged, and wants to undermine the Count’s plans (Se vuol ballare).
Bartolo, and his housekeeper Marcellina arrive, and Marcellina is discussing her legal matters with Bartolo, who she has hired as legal counsel. Figaro had once promised Marcellina to marry her if she would forget about a loan she had given him, and she wants to steal him from Susanna. Bartolo is in on the plan because he is still mad at Figaro for setting up the Count and Rosina and wants to get vengence (La vendetta). Bartolo leaves, but Susanna runs into Marcellina. The two being rivals, share a duet in which they hurl overly polite sarcastic insults at one another (Via resti servita, madama brillante). Cherubino arrives after Marcellina runs off in a rage, and tells Susanna about how he is enchanted by all women, especially the Countess (Non so più cosa son). Cherubino asks for Susanna’s help because the Count wants to send Cherubino away after having found him with the gardener’s daughter, Barbarina. The Count comes by to see Susanna, and Cherubino hides behind a chair, not wanting to be caught with Susanna alone, even though nothing inappropriate happened. The Count, having Susanna alone, tries to get her to