Happy-go-lucky Figaro, roving barber of Seville, is strolling the streets with his guitar when he chances upon a former employer, the young Count Almaviva, and consequently a problem in romance well suited to his roguish wit. The Count has seen and fallen in love with Rosine, a beautiful young lady who is the ward and unwilling fiancée of Dr. Bartholo, an old tyrant who generally keeps her well concealed behind locked doors.
Disguised as a poor student, the Count comes each morning to glimpse Rosine when she can elude Bartholo and appear at her window. It is here beneath her window that he has met Figaro. Rosine has just managed to drop a note written on the score of a song. "The Useless Precaution." It reads: "I don't know who you are, but your devotion excites my curiosity.... Sing a few words to the tune of the song on this sheet. Disclose your name, your rank and your intentions to the unfortunate Rosine." He takes Figaro's guitar and sings: "My name is Lindor, sweet, and I adore thee!" She replies: "Thy love and adoration I return...."
The elated Count declares that he must save her from Dr. Bartholo, and Figaro, warning that Bartholo plans to wed Rosine the next day, offers a plan: Figaro is the Doctor's apothecary as well as his barber, and he will drug the servants; then the Count can enter the house in the guise of an army officer who must have lodging but is apparently too drunk to wish for flirtation. This is agreed upon after Figaro, holding out his hand, observes: "It is gold that greases the wheels of love."
Next, Figaro is waiting in Rosine's room while she writes a note to the presumed poor student, Lindor. He hides in a closet when Bartholo appears to voice suspicion that the barber has drugged the servants. The Doctor says he is going to lock her window blind now, and she flounces from the room as Don Bazile, her music teacher, comes to warn Bartholo that Count Almaviva is walking the streets in disguise, evidently seeking Rosine. He advises Bartholo to slander Lindor and agrees to arrange the wedding, but he hints that "gold makes the strongest link in the matrimonial chain."
Figaro slips out to urge the Count to hasten, and Almaviva soon appears at Bartholo's house in the role of a drunken trooper. He whispers to Rosine that he is Lindor and hands her a letter; but, after outraging Bartholo with his jeers, he is ordered out of the house. Bartholo demands the letter, but Rosine deftly exchanges it for a harmless note from her cousin. Bartholo then leaves. Rosine reads Almaviva's note and exclaims: "Ah, it's too late! He asked me to start a quarrel with my guardian, so he could carry me off in the scuffle.... Now he is gone and I'm to be wedded to my evil fate.... What shall I do?"
But the Count tries again, in a new disguise. He tells Bartholo that Bazile is ill and that he, his pupil, has come to help prepare for the marriage. Bartholo urges that he allay any suspicions Rosine may have by saying he has come to give her a music lesson. The Count happily agrees, but the jealous Doctor seats himself before them. He nods sleepily, however, and the Count again identifies himself to Rosine as Lindor. Their kisses awaken Bartholo, and Figaro comes to the rescue.
He suggests that Bartholo go with him to be shaved, but the Doctor orders that he be shaved where he is, and gives Figaro his keys to fetch the utensils. Behind his back, Figaro winks and holds aloft the key to the window blind. Then, by making a clatter in Bartholo's room, he lures the Doctor out to investigate. The Count hurriedly whispers: "Good old Figaro!... You are going to escape tonight, through your window. He will unlock your blind with that key which he showed us."
Bartholo and Figaro have returned, the barber again making meaningful gestures with the key, when another crisis confronts the conspirators: Bazile enters. Bartholo tells him that "his pupil" has reported him ill, and Bazile exclaims: "This young man?" He is further confused when Bartholo, at the Count's whispered warning that "Rosine mustn't suspect anything, you know," enjoins Bazile in another aside: "Don't say that he is not your pupil. Rosine must be kept in the dark."
When Rosine adds to his confusion with another whisper: "The less you say, the better," Don Bazile whispers to Figaro: "What the devil is the meaning of this? Everybody seems to have a secret." The Count breaks the chain of whispers by handing Bazile a purse and telling him: "Go to bed. You're sick." This cue is joyously received by all the plotters who chorus that Bazile indeed looks sick and should go to bed. Bazile agrees that, come to think of it, he does feel rather funny. He leaves abruptly.
Figaro begins to shave Bartholo, standing between him and the lovers, but the wary Doctor spies them as they are about to embrace and shouts an accusation. Rosine leaves angrily, and Figaro says: "I don't blame her. A young woman and an old man! Why, sir, you're mad!" He goes out. The Count declares: "I quite agree with Figaro; old man, you're mad." He, too, departs. Now Bartholo, distrusting his own eyes, wonders if he really did see them embrace. Suspecting, too, that he may be going mad, he calls for Bazile.
It is nearly midnight, and he orders Bazile to bring the notary to marry him and Rosine before morning. Bazile tells him that the notary can't come before four o'clock as he has to marry Figaro's niece. Bartholo's suspicions are now confirmed, since he knows Figaro has no niece. To spoil the plot, he tells Rosine that Lindor is untrue to her and is making sport of her love by giving her letters to Count Almaviva. Rosine believes him, and in her humiliation confesses that she and Lindor were to escape that night through the window, but that she will marry her guardian instead. Bartholo gleefully goes off to bring the police to trap Lindor.
While he is absent, the Count and Figaro enter through the window, and the reproachful Rosine is startled to learn that her lover is not the poor student Lindor but the noble, Count Almaviva. Don Bazile returns with the notary, and the Count instructs the official to marry him to Rosine. The protesting Bazile, handed the Count's purse, says: "I'm always convinced by a heavy argument."
The ceremony is no sooner over when Bartholo bustles in with the police. He cries: "What's this? You have stolen my bride?" The Count replies: "Yes, and you have stolen her property." Bartholo calls him an impertinent young student," and Figaro warns: "Be careful, you are speaking to his Excellency, the Lord Count Almaviva." Bartholo quickly protests that he is the Count's humble servant and Almaviva shows mercy: he could have Bartholo arrested for misuse of his ward's money, he declares, but he will let him keep the fortune if he will withdraw his claim upon Rosine.