Place: A small village in the Basque Country
Time: The end of the 18th century
Act 1
Nemorino, a poor peasant, is in love with Adina, a beautiful landowner, who torments him with her indifference. When Nemorino hears Adina reading to her workers the story of Tristan and Isolde, he is convinced that a magic potion will help him to gain Adina's love. The self-important Sergeant Belcore appears with his regiment and immediately sets about courting Adina in front of everyone. Nemorino becomes anxious (although, Adina meanwhile secretly derides Belcore's complacency) and, alone with Adina, reveals his love for her. Yet Adina rebuffs him, saying she wants a different lover every day and following her example would do Nemorino better. Nemorino declares that his feelings will never change. The travelling quack doctor, Dulcamara (the self-proclaimed Dr. Encyclopedia), arrives, selling his bottled cure-all to the townspeople. Nemorino innocently asks Dulcamara if he has any of Isolde's love potion. Despite failing to recognise the name "Isolde", Dulcamara's commercial talents nevertheless enable him to sell a bottle of the cure-all – in reality only cheap wine – to Nemorino, withdrawing all his savings.
To make a safe escape, Dulcamara tells Nemorino the potion needs 24 hours to take effect – by which time, the doctor will be long gone. Nemorino drinks the potion in a haste in order to watch the effect tomorrow. Emboldened by the "elixir" (in fact, drunk), Nemorino feigns indifference when he encounters Adina, as he expects that the elixir will facilitate his conquest of Adina the following day. She becomes increasingly annoyed; perhaps she has feelings for Nemorino after all? Belcore returns and proposes marriage to Adina. Still riled by Nemorino and wishing to give him a lesson, Adina falsely promises to marry Belcore in six days' time. Yet Nemorino only laughs in response: such confidence is sustained in the belief in the magic potion. However, when Belcore learns that his regiment must leave the next morning, Adina promises to marry him before his departure. This of course panics Nemorino, who cries out for Dr. Dulcamara to come to his aid. Adina, meanwhile, invites everyone to the wedding.
Act 2
Adina and Belcore's wedding party is in full swing. Dr. Dulcamara encourages Adina to sing a duet with him to entertain the guests. The notary arrives to make the marriage official. Adina is annoyed to see that Nemorino has not appeared, for the whole deal has been intended only to punish him. While everyone goes to witness the signing of the wedding contract, Dulcamara stays behind, helping himself to food and drink. Having seen the notary, Nemorino appears, depressed, as he believes that he has lost Adina. He sees Dulcamara and frantically begs him for a more powerful, faster-acting elixir. Although Dulcamara is proud to boast of his philanthropy, upon discovering that Nemorino now has no money he changes his tune and marches off, refusing to supply him anything. Belcore emerges, musing about why Adina has suddenly put off the wedding and signing of the contract. He spots Nemorino and asks his rival why he is depressed. When Nemorino says he needs cash, Belcore suggests joining the army, as he'll receive funds on the spot. Belcore tries to excite Nemorino with tales of military life, while Nemorino only thinks of getting the potion and thus winning Adina, if only for a day before departure. Belcore produces a contract, which Nemorino signs in return for the money. Nemorino privately vows to rush and buy more potion, while Belcore muses about how sending Nemorino off to war has so easily dispatched his rival.
After the two men have left, Giannetta gossips with the women of the village. Swearing them all to secrecy, she reveals that Nemorino's uncle has just died and left his nephew a large fortune. However, neither Nemorino nor Adina is yet aware of this. Nemorino enters, having spent his military signing bonus on – and consumed – a large amount of the fake elixir from Dr. Dulcamara. Hoping to share his fortune, the women approach Nemorino with overly friendly greetings. So out of character is this that Nemorino takes it as proof of the elixir's efficacy. Adina sees Nemorino with the women, is rattled by his newfound popularity, and asks Dr. Dulcamara for an explanation. Unaware that Adina is the object of Nemorino's affection, Dulcamara explains that Nemorino spent his last penny on the elixir and joined the army for money to get more, so desperate was he to win the love of some unnamed cruel beauty. Adina immediately recognises Nemorino's sincerity, regrets her behaviour and realises that she has loved Nemorino all along. Although Dulcamara seizes the opportunity to try to sell her some of his potion to win back Nemorino, Adina declares that she has full confidence in her own powers of attraction.
Nemorino appears alone, pensive, reflecting on a tear he saw in Adina's eye when he was ignoring her earlier. Solely based on that, he convinces himself that Adina loves him. She enters and asks why he has chosen to join the army and leave the village. When Nemorino explains that he was seeking a better life, Adina responds that he is loved and that she has purchased back his military contract from Sergeant Belcore. She offers the cancelled contract to Nemorino and reassures him that, if he stays, he will be happy. As he takes the contract, Adina turns to leave. Nemorino believes she is abandoning him and flies into a desperate fit, vowing that if he is not loved he might as well go off and die a soldier. Deeply moved by his fidelity, Adina finally declares that she will love Nemorino forever. Nemorino is ecstatic. Adina begs him to forgive her, which he does with a kiss. Belcore returns to see Nemorino and Adina in an embrace. When Adina explains that she loves Nemorino, the Sergeant takes the news in stride, noting that there are plenty of other women in the world. Adina and Nemorino learn about the inheritance from his uncle. Dulcamara returns and boasts of the success of his elixir: Nemorino is now not only loved but also rich. He exults in the boost this will bring to the sales of his product. As he prepares to leave, everyone queues up to buy the elixir and hails Dulcamara as a great physician.

Place: Paris and its vicinity
Time: Beginning of the 19th century
Act 1
The salon in Violetta's house
Violetta Valéry, a famed courtesan, throws a lavish party at her Paris salon to celebrate her recovery from an illness. Gastone, a viscount, has brought with him a friend, Alfredo Germont, a young bourgeois from a provincial family who has long adored Violetta from afar. While walking to the salon, Gastone tells Violetta that Alfredo loves her, and that while she was ill, he came to her house every day. Alfredo joins them, admitting the truth of Gastone's remarks.
Baron Douphol, Violetta's current lover, waits nearby to escort her to the salon; once there, the Baron is asked to give a toast, but refuses, and the crowd turns to Alfredo, who agrees to sing a brindisi – a drinking song (Alfredo, Violetta, chorus: Libiamo ne' lieti calici – "Let's drink from the joyful cups").
From the next room, the sound of the orchestra is heard and the guests move there to dance. After a series of severe coughs and almost fainting, Violetta begins to feel dizzy and asks her guests to go ahead and to leave her to rest until she recovers. While the guests dance in the next room, Violetta looks at her pale face in her mirror. Alfredo enters and expresses his concern for her fragile health, later declaring his love for her (Alfredo, Violetta: Un dì, felice, eterea – "One day, happy and ethereal"). At first, she rejects him because his love means nothing to her, but there is something about Alfredo that touches her heart. He is about to leave when she gives him a flower, telling him to return it when it has wilted, which will be the very next day.
After the guests leave, Violetta wonders if Alfredo could actually be the one in her life (Violetta: È strano! ... Ah, fors' è lui – "Ah, perhaps he is the one"). But she concludes that she needs freedom to live her life (Violetta, Alfredo: Sempre libera – "Always free"). From off stage, Alfredo's voice is heard singing about love as he walks down the street.
Act 2
Scene 1: Violetta's country house outside Paris
Three months later, Alfredo and Violetta are living together in a peaceful country house outside Paris. Violetta has fallen in love with Alfredo and she has completely abandoned her former life. Alfredo sings of their happy life together (Alfredo: De' miei bollenti spiriti / Il giovanile ardore – "The youthful ardor of my ebullient spirits"). Annina, the maid, arrives from Paris, and, when questioned by Alfredo, tells him that she went there to sell the horses, carriages and everything owned by Violetta to support their country lifestyle.
Alfredo is shocked to learn this and leaves for Paris immediately to settle matters himself. Violetta returns home and receives an invitation from her friend, Flora, to a party in Paris that evening. Alfredo's father, Giorgio Germont, is announced and demands that she break off her relationship with his son for the sake of his family, since he reveals that Violetta's relationship with Alfredo has threatened his daughter's engagement (Giorgio: Pura siccome un angelo, Iddio mi diè una figlia – "Pure as an angel, God gave me a daughter") because of Violetta's reputation. Meanwhile, he reluctantly becomes impressed by Violetta's nobility, something which he did not expect from a courtesan. She responds that she cannot end the relationship because she loves him so much, but Giorgio pleads with her for the sake of his family. With growing remorse, she finally agrees (Violetta, Giorgio: Dite alla giovine, sì bella e pura, – "Tell the young girl, so beautiful and pure,") and says goodbye to Giorgio. In a gesture of gratitude for her kindness and sacrifice, Giorgio kisses her forehead before leaving her weeping alone.
Violetta gives a note to Annina to send to Flora accepting the party invitation and, as she is writing a farewell letter to Alfredo, he enters. She can barely control her sadness and tears; she tells him repeatedly of her unconditional love (Violetta: Amami, Alfredo, amami quant'io t'amo – "Love me, Alfredo, love me as I love you"). Before rushing out and setting off for Paris, she hands the farewell letter to her servant to give to Alfredo.
Soon, the servant brings the letter to Alfredo and, as soon as he has read it, Giorgio returns and attempts to comfort his son, reminding him of his family in Provence (Giorgio: Di Provenza il mar, il suol chi dal cor ti cancellò? – "Who erased the sea, the land of Provence from your heart?"). Alfredo suspects that the Baron is behind his separation with Violetta, and the party invitation, which he finds on the desk, strengthens his suspicions. He decides to confront Violetta at the party. Giorgio tries to stop Alfredo, but he rushes out.
Scene 2: Party at Flora's house
At the party, the Marquis tells Flora that Violetta and Alfredo have separated, much to the amazement of everyone who had previously seen the happy couple. She calls for the entertainers to perform for the guests (Chorus: Noi siamo zingarelle venute da lontano – "We are gypsy girls who have come from afar"; Di Madride noi siam mattadori – "We are matadors from Madrid"). Gastone and his friends join the matadors and sing (Gastone, chorus, dancers: È Piquillo un bel gagliardo Biscaglino mattador – "Piquillo is a bold and handsome matador from Biscay").
Violetta arrives with Baron Douphol. They see Alfredo at the gambling table. When he sees them, Alfredo loudly proclaims that he will take Violetta home with him. Feeling annoyed, the Baron goes to the gambling table and joins him in a game. As they bet, Alfredo wins some large sums until Flora announces that supper is ready. Alfredo leaves with handfuls of money.
As everyone is leaving the room, Violetta has asked Alfredo to see her. Fearing that the Baron's anger will lead him to challenge Alfredo to a duel, she gently asks Alfredo to leave. Alfredo misunderstands her apprehension and demands that she admit that she loves the Baron. In grief, she makes that admission and, furiously, Alfredo calls the guests to witness what he has to say (Questa donna conoscete? – "You know this woman?"). He humiliates and denounces Violetta in front of the guests and then throws his winnings at her feet in payment for her services. She faints onto the floor. The guests reprimand Alfredo: Di donne ignobile insultatore, di qua allontanati, ne desti orror! ("Ignoble insulter of women, go away from here, you fill us with horror!").
In search of his son, Giorgio enters the hall and, knowing the real significance of the scene, denounces his son's behavior (Giorgio, Alfredo, Violetta, chorus: Di sprezzo degno sè stesso rende chi pur nell'ira la donna offende. – "A man, who even in anger, offends a woman renders himself deserving of contempt.").
Flora and the ladies attempt to persuade Violetta to leave the dining room, but Violetta turns to Alfredo: Alfredo, Alfredo, di questo core non puoi comprendere tutto l'amore... – "Alfredo, Alfredo, you can't understand all the love in this heart...".
Act 3
Violetta's bedroom
Dr. Grenvil tells Annina that Violetta will not live long since her tuberculosis has worsened. Alone in her room, Violetta reads a letter from Alfredo's father telling her that the Baron was only wounded in his duel with Alfredo. He has informed Alfredo of the sacrifice she has made for him and his sister; and that he is sending his son to see her as quickly as possible to ask for her forgiveness. But Violetta senses it is too late (Violetta: Addio, del passato bei sogni ridenti – "Farewell, lovely, happy dreams of the past").
Annina rushes in the room to tell Violetta of Alfredo's arrival. The lovers are reunited and Alfredo suggests that they leave Paris (Alfredo, Violetta: Parigi, o cara, noi lasceremo – "We will leave Paris, O beloved").
But it is too late: she knows her time is up (Alfredo, Violetta: Gran Dio!...morir sì giovane – "Great God!...to die so young"). Alfredo's father enters with the doctor, regretting what he has done. After singing a duet with Alfredo, Violetta suddenly revives, exclaiming that the pain and discomfort have left her. A moment later, she dies in Alfredo's arms.