The Marriage of Figaro begins on the wedding day of Figaro and Suzanne. Suzanne reveals to her fiancé that the Count has offered her a dowry in exchange for spending the first night with him. Figaro realizes he must act swiftly to thwart the Count's intentions. He decides to deceive the Count by advancing the time of the wedding. Simultaneously, he must fend off Marceline, who wishes to marry him. Marceline has enlisted Bartholo in her scheme to win over Figaro, which includes encouraging the Count to oppose Suzanne and Figaro's marriage.

While alone in her room, Suzanne is visited by Cherubino, who has been dismissed by the Count after being caught in Fanchette's room. Cherubino asks Suzanne to convince the Count to reinstate him. The Count's sudden arrival forces Cherubino to hide behind a chair, where he overhears the Count asking Suzanne to meet him later to discuss spending the night together. When Basil enters the room, the Count hides behind the chair, and Cherubino climbs atop it. Basil advises Suzanne to give in to the Count and reveals Cherubino's affection for the Countess, prompting the Count to reveal himself. He orders Cherubino to be dismissed permanently. However, under pressure from the household, he decides to give Cherubino a commission in the army instead of expelling him. Figaro needs Cherubino for his plan to thwart the Count, so he tells the page to return to the castle immediately. Meanwhile, the Count hopes Marceline will assist him in preventing the marriage.