Act I
It is the wedding day of Figaro, Count Almaviva´s faithful servant. He is to marry the mischievous Susanna, personal maid to the Countess.
There is no doubt that the wedding will not pass without incident, because the Count is involved! Even the matter of his wedding gift to the young couple is not without its complications: they have been promised a room linking his apartments with those of the Countess. So convenient – if either of them is needed, they can be on the spot in a moment. Figaro is pleased, but Susanna… Susanna has her suspicions. After all, if the room is so convenient, it means the Count can get to her: Almaviva, she says, wishes to make use of the right to "the first night", the famous "droit de Seigneur" by which landlords may enjoy all the brides on their estates on their wedding night – before the husband may do so.
Figaro cannot believe his ears. After he married the beautiful Rosina, the Count promised to renounce this ancient right. But Figaro is not about to let himself be taken for a ride. He´s a good servant, but he is not prepared to stand by and be ridden over roughshod.
The marriage is opposed by the ageing duenna Marcellina and her former admirer, Doctor Bartolo. Bartolo can never forget how the cunning Barber of Seville–as Figaro was known at that time–made a fool of him when bringing together Almaviva and Rosina. Now the vengeful old man wishes to get his own back. Marcellina, meanwhile, lent Figaro money in return for a written promise to marry her if he did not repay it. Bartolo hopes to do his worst against the hated Figaro by forcing him to marry Marcellina, even though the duenna still has the power to arouse feelings in him.
Susanna, meanwhile, listens as the young page Cherubino tells of his love for the Countess. But not for her alone. The youth is in love with all the women in the castle and keeps finding himself in all sorts of unfortunate situations. Just recently, the Count found him alone with Barbarina, the young the niece of the gardener Antonio, and gave orders that the boy be expelled from the castle. Only the intervention of the Countess can soothe Almaviva´s anger and Cherubino asks Susanna to put in a good word for him with her mistress. But the Count himself appears at this moment. Hearing his approach, Cherubino hides in fright and thus involuntarily becomes a witness as Almaviva begs of Susanna a meeting. But his Grace too is forced to follow the page´s example, for in comes the music master, don Basilio, and the Count has no desire to be caught alone with Susanna. He too hides. Don Basilio relates the story of Cherubino´s love for the Countess and, beside himself; the Count leaps form his hiding place. His anger grows when he sees Cherubino.
Things are not going well for the page, but Susanna comes to his aid. Hinting that Cherubino has witnessed the Count´s outpourings. The girl manages to calm her master´s anger. Almaviva´s embarrassment increases when he is forced to listen to the assembled peasants who have come to thank their Lord for renouncing his "droit de Seigneur". It is Figaro who has brought them to the castle in an effort to push forward his wedding to Susanna. Almaviva is forced to agree to the wedding and agrees to be a guest at the celebrations. Taking advantage of the Count´s confusion, Cherubino manages to gain his pardon, but only on condition that he join the army immediately. Figaro sets out before the pampered page all the "horrors" of military service.

Act II
The Countess´s Room
Susanna, the Countess and Figaro have decided to teach the Count a lesson. Susanna is to promise him a rendezvous but Cherubino will appear in her place, wearing her dress. Cherubino has the dress on when Almaviva is heard and the page is forced to hide in the neighboring room. But the Count notices that the door of the room is locked. He demands that the Countess give him the key, and when she refuses to give it to him, he goes off to get tools to break the door down, insisting that the Countess accompany him. Susanna immediately takes Cherubino´s place in the room, the page jumping from the window. The Count returns triumphant – now he can prove that his wife has been unfaithful. The door is broken open and Susanna emerges from the room. Covered in shame. Almaviva is forced to beg his wife´s pardon. But then the gardener Antonio unexpectedly appears with a broken flowerpot – someone just jumped from the window, he says, and damaged his flowers. Figaro comes to the rescue of the Countess and Susanna, declaring that it was he, again forcing the Count to apologize. Enter Bartolo, Don Basilio and Marcellina, come to lodge the old duenna´s claim for breach of promise. Figaro has no money to pay his debt – and he is to answer before a court.

Act III
A room in the castle
The court (in the person of Count) has made its decision in favor of Marcellina. Figaro is saved, however, when it becomes clear that he is in fact the son of Marcellina and Bartolo, who was stolen as a baby. The joyful parents decide to celebrate their wedding along with that of their newly found son.
During the wedding celebrations Figaro notices that the Count is reading a note. In it Susanna has appointed a meeting with the Count. She has agreed to change dresses with the Countess, and so the woman who will meet the Count in his garden that night will in fact be his wife. The note is sealed with a pin. If the Count agrees to be in the appointed place at the appointed time, he must return the pin to Susanna. Figaro, unaware of his wife´s plot, becomes suspicious and decides to follow the Count´s movements.

Act IV
The garden of Almaviva´s castle
In the moonlight, Barbarina is looking for a pin she has lost in the grass. In answer to Figaro´s question as to what she is doing, she answers that the Count has ordered her to deliver the pin to Susanna. Taken aback at his bride´s lack of faith, Figaro decides to lie in wait for the Count and Susanna. Susanna appears in the Countess´s dress – which leads to a multitude of misunderstandings. But all comes right in the end. The Count begs his wife´s forgiveness and the Countess grants it.
A day of commotion and confusion draws to a close in merry celebrations.

The play is set at the castle of Aguas Frescas, three leagues from Seville.

Act I

The play begins in a room in the Count's castle—the bedroom to be shared by Figaro and Suzanne after their wedding, which is set to occur later that day. Suzanne reveals to Figaro her suspicion that the Count gave them this particular room because it is so close to his own, and that the Count has been pressing her to begin an affair with him. Figaro at once goes to work trying to find a solution to this problem. Then Dr. Bartholo and Marceline pass through, discussing a lawsuit they are to file against Figaro, who owes Marceline a good deal of money and has promised to marry her if he fails to repay the sum; his marriage to Suzanne will potentially void the contract. Bartholo relishes the news that Rosine is unhappy in her marriage, and they discuss the expectation that the Count will take Figaro's side in the lawsuit if Suzanne should submit to his advances. Marceline herself is in love with Figaro, and hopes to discourage Suzanne from this.

After a brief confrontation between Marceline and Suzanne, a young pageboy named Chérubin comes to tell Suzanne that he has been dismissed for being caught hiding in the bedroom of Fanchette. The conversation is interrupted by the entrance of the Count, and since Suzanne and Chérubin do not want to be caught alone in a bedroom together, Chérubin hides behind an armchair. When the Count enters, he propositions Suzanne (who continues to refuse to sleep with him). They are then interrupted by Bazile's entrance. Again, not wanting to be found in a bedroom with Suzanne, the Count hides behind the armchair. Chérubin is forced to throw himself on top of the armchair so the Count will not find him, and Suzanne covers him with a dress so Bazile cannot see him. Bazile stands in the doorway and begins to tell Suzanne all the latest gossip. When he mentions a rumour that there is a relationship between the Countess and Chérubin, the Count becomes outraged and stands up, revealing himself. The Count justifies his firing Chérubin to Bazile and the horrified Suzanne (now worried that Bazile will believe that she and the Count are having an affair). The Count re-enacts finding Chérubin behind the door in Fanchette's room by lifting the dress covering Chérubin, accidentally uncovering Chérubin's hiding spot for the second time. The Count is afraid that Chérubin will reveal the earlier conversation in which he was propositioning Suzanne, and so decides to send him away at once as a soldier. Figaro then enters with the Countess, who is still oblivious to her husband's plans. A troupe of wedding guests enters with him, intending to begin the wedding ceremony immediately. The Count is able to persuade them to hold it back a few more hours, giving himself more time to enact his plans.

Act II
The scene is the Countess's bedroom. Suzanne has just broken the news of the Count's action to the Countess, who is distraught. Figaro enters and tells them that he has set in motion a new plan to distract the Count from his intentions toward Suzanne by starting a false rumour that the Countess is having an affair and that her lover will appear at the wedding; this, he hopes, will motivate the Count to let the wedding go ahead. Suzanne and the Countess have doubts about the effectiveness of the plot; they decide to tell the Count that Suzanne has agreed to his proposal, and then to embarrass him by sending out Chérubin dressed in Suzanne's gown to meet him. They stop Chérubin from leaving and begin to dress him, but just when Suzanne steps out of the room, the Count comes in. Chérubin hides, half dressed, in the adjoining dressing room while the Count grows increasingly suspicious, especially after having just heard Figaro's rumour of the Countess's affair. He leaves to get tools to break open the dressing room door, giving Chérubin enough time to escape through the window and Suzanne time to take his place in the dressing room; when the Count opens the door, it appears that Suzanne was inside there all along. Just when it seems he calms down, the gardener Antonio runs in screaming that a half-dressed man just jumped from the Countess's window. The Count's fears are settled again once Figaro takes credit to being the jumper, claiming that he started the rumour of the Countess having an affair as a prank and that while he was waiting for Suzanne he became frightened of the Count's wrath, jumping out the window in terror. Just then Marceline, Bartholo and the judge Brid'oison come to inform Figaro that his trial is starting.

Act III
Figaro and the Count exchange a few words, until Suzanne, at the insistence of the Countess, goes to the Count and tells him that she has decided that she will begin an affair with him, and asks he meet her after the wedding. The Countess has actually promised to appear at the assignation in Suzanne's place. The Count is glad to hear that Suzanne has seemingly decided to go along with his advances, but his mood sours again once he hears her talking to Figaro and saying it was only done so they might win the case.

Court is then held, and after a few minor cases, Figaro's trial occurs. Much is made of the fact that Figaro has no middle or last name, and he explains that it is because he was kidnapped as a baby and doesn't know his real name. The Count rules in Marceline's favour, effectively forcing Figaro to marry her, when Marceline suddenly recognizes a birthmark (or scar or tattoo; the text is unclear) in the shape of a spatule (lobster) on Figaro's arm—he is her son, and Dr. Bartholo is his father. Just then Suzanne runs in with enough money to repay Marceline, given to her by the Countess. At this, the Count storms off in outrage.

Figaro is thrilled to have rediscovered his parents, but Suzanne's uncle, Antonio, insists that Suzanne cannot marry Figaro now, because he is illegitimate. Marceline and Bartholo are persuaded to marry in order to correct this problem.

Act IV
Figaro and Suzanne talk before the wedding, and Figaro tells Suzanne that if the Count still thinks she is going to meet him in the garden later, she should just let him stand there waiting all night. Suzanne promises, but the Countess grows upset when she hears this news, thinking that Suzanne is in the Count's pocket and is wishing she had kept their rendezvous a secret. As she leaves, Suzanne falls to her knees, and agrees to go through with the plan to trick the Count. Together they write a note to him entitled "A New Song on the Breeze" (a reference to the Countess's old habit of communicating with the Count through sheet music dropped from her window), which tells him that she will meet him under the chestnut trees. The Countess lends Suzanne a pin from her dress to seal the letter, but as she does so, the ribbon from Chérubin falls out of the top of her dress. At that moment, Fanchette enters with Chérubin disguised as a girl, a shepherdess, and girls from the town to give the Countess flowers. As thanks, the Countess kisses Chérubin on the forehead. Antonio and the Count enter—Antonio knows Chérubin is disguised because they dressed him at his daughter's (Fanchette's) house. The Countess admits to hiding Chérubin in her room earlier and the Count is about to punish him. Fanchette suddenly admits that she and the Count have been having an affair, and that, since he has promised he will give her anything she desires, he must not punish Chérubin but give him to her as a husband. Later, the wedding is interrupted by Bazile, who had wished to marry Marceline himself; but once he learns that Figaro is her son he is so horrified that he abandons his plans. Later, Figaro witnesses the Count opening the letter from Suzanne, but thinks nothing of it. After the ceremony, he notices Fanchette looking upset, and discovers that the cause is her having lost the pin that was used to seal the letter, which the Count had told her to give back to Suzanne. Figaro nearly faints at the news, believing Suzanne's secret communication means that she has been unfaithful and, restraining tears, he announces to Marceline that he is going to seek vengeance on both the Count and Suzanne.

Act V

In the castle gardens beneath a grove of chestnut trees, Figaro has called together a group of men and instructs them to call together everyone they can find: he intends to have them all walk in on the Count and Suzanne in flagrante delicto, humiliating the pair and also ensuring ease of obtaining a divorce. After a tirade against the aristocracy and the unhappy state of his life, Figaro hides nearby. The Countess and Suzanne then enter, each dressed in the other's clothes. They are aware that Figaro is watching, and Suzanne is upset that her husband would doubt her so much as to think she would ever really be unfaithful to him. Soon afterward the Count comes, and the disguised Countess goes off with him. Figaro is outraged, and goes to the woman he thinks is the Countess to complain; he realises that he is talking to his own wife Suzanne, who scolds him for his lack of confidence in her. Figaro agrees that he was being stupid, and they are quickly reconciled. Just then the Count comes out and sees what he thinks is his own wife kissing Figaro, and races to stop the scene. At this point, all the people who had been instructed to come on Figaro's orders arrive, and the real Countess reveals herself. The Count falls to his knees and begs her for forgiveness, which she grants. After all other loose ends are tied up, the cast breaks into song before the curtain falls.

Figaro's speech
One of the defining moments of the play—and Louis XVI's particular objection to the piece—is Figaro's long monologue in the fifth act, directly challenging the Count:

No, my lord Count, you shan't have her... you shall not have her! Just because you are a great nobleman, you think you are a great genius—Nobility, fortune, rank, position! How proud they make a man feel! What have you done to deserve such advantages? Put yourself to the trouble of being born—nothing more. For the rest—a very ordinary man! Whereas I, lost among the obscure crowd, have had to deploy more knowledge, more calculation and skill merely to survive than has sufficed to rule all the provinces of Spain for a century!
[...]
I throw myself full-force into the theatre. Alas, I might as well have put a stone round my neck! I fudge up a play about the manners of the Seraglio; a Spanish author, I imagined, could attack Mahomet without scruple; but immediately some envoy from goodness-knows-where complains that some of my lines offend the Sublime Porte, Persia, some part or other of the East Indies, the whole of Egypt, the kingdoms of Cyrenaica, Tripoli, Tunis, Algiers and Morocco. Behold my comedy scuppered to please a set of Mohammedan princes—not one of whom I believe can read—who habitually beat a tattoo on our shoulders to the tune of "Down with the Christian dogs!" Unable to break my spirit, they decided to take it out on my body. My cheeks grew hollowed: my time was out. I saw in the distance the approach of the fell sergeant, his quill stuck into his wig.
[...]
I'd tell him that stupidities acquire importance only in so far as their circulation is restricted, that unless there is liberty to criticize, praise has no value, and that only trivial minds are apprehensive of trivial scribbling