The servants and fiancés Susanna and Figaro are up at dawn, busily preparing for married life. Figaro readies the space for the bed the Count has generously promised them, and Susanna deliberates about what to wear to their wedding. She reminds her husband-to-be that the Count’s gesture is not so selfless at all: he fancies her and will do whatever he can to get her into bed while he still can. The Count unexpectedly acquires a pair of allies: Marcellina and Bartolo, an offbeat older couple. They apparently once had an affair, but more importantly, Figaro has an unpaid debt with Marcellina, and she has come to collect. One condition of the loan was that if he defaulted, he would have to marry her. Bartolo has a bone of his own to pick with Figaro, so he gladly offers Marcellina legal assistance in her case against Figaro.
Then there is Cherubino, the adolescent page bursting with sexual yearnings and who falls for practically every woman he meets. The Count has already caught Cherubino with Barbarina (the daughter of the gardener from Act II) and will not tolerate competition for the attentions of the females on the estate. Just as Cherubino turns to Susanna for help, who should show up in her chamber unannounced but the amorous Count. The startled page hides, hears something he probably shouldn’t have, and is again nabbed by the Count. (This is all quite amusing to Basilio, who sees that his job – stoking intrigue amongst the castle residents – is being done for him.) To be rid of the frisky young rascal once and for all, the Count sends Cherubino to join the army. As this first act draws to a close, Figaro – backed by a group of locals he has drummed up for this effort – attempts to get the Count to abandon his designs on his fiancée and presses for a speedy marriage between him and Susanna.