Plot
The film is set in the year 1900, during the Belle Époque at the turn of the 20th century. While in the Bois de Boulogne, Honoré Lachaille remarks that in Paris, marriage is not the sole option for wealthy young bon vivants like his nephew Gaston, who is bored with life. Gaston does enjoy spending time with Madame Alvarez and her granddaughter, precocious, carefree Gilberte, affectionately known as Gigi. Gigi's mother (a singer who is heard but never seen onscreen) leaves her care mostly to Madame Alvarez.
Following the "family tradition", Madame Alvarez regularly sends Gigi to her sister and Gigi's great-aunt, Alicia, to be groomed as a courtesan, a kept mistress of wealthy men. Gigi learns proper etiquette and charm but disdains the trivial love between a man and his mistress. She prefers to have fun with Gaston, whom she regards as an older brother or a young uncle.
Like his uncle, Gaston is a known wealthy womanizer in Parisian high society. When his latest mistress has an affair with her ice-skating instructor, Gaston publicly humiliates her, resulting in her fake attempted suicide. Gaston plans to retreat to the country, but his uncle insists that he remain in Paris and attend even more parties.
While playing cards with Gaston, Gigi wagers that if he loses, he must take her and her grandmother to the seaside for the weekend. Gaston loses the bet, and the three travel to Trouville. While Gaston and Gigi have fun together, Honoré and Madame Alvarez unexpectedly reunite and reminisce about their once-passionate affair.
When Gaston goes to Monte Carlo, Great-Aunt Alicia and Madame Alvarez scheme to turn Gigi into Gaston's mistress. Though initially dubious, Madame Alvarez agrees to Gigi being intensively trained before Gaston's return. Gigi accepts this as pre-destined.
When Gaston returns, he is discomfited when Gigi shows off her new womanly gown. Gaston insults the dress, preferring her juvenile outfits; Gigi mocks his taste in clothes. Offended, Gaston storms out, then realizes his folly and returns to apologize. He offers to take Gigi to tea at the Reservoir, but Madame Alvarez tells him that an unchaperoned Gigi being seen in public with him could damage her reputation.
Angered, Gaston storms out again. He reflects on Gigi, realizing he has developed a romantic desire for her. Although hesitant due to her young age, Gaston realizes that he loves Gigi. He proposes a generous "business arrangement" to Madame Alvarez and Aunt Alicia for Gigi to become his mistress. Gigi refuses, telling Gaston she does not seek celebrity status, only to eventually be abandoned by him and become another man's mistress. She wants their relationship to remain platonic, but when Gaston reveals that he is in love with her, Gigi is horrified. She calls Gaston a wicked man for claiming to love her while still proposing this arrangement before fleeing the room in tears. Gaston chastises Madame Alvarez for exposing Gigi to the sordid details of his lifestyle, then leaves. Gigi later sends for Gaston and tells him that she would rather be miserable with him than without him, agreeing to the arrangement.
The couple go to Maxim's restaurant. Gigi performs perfectly as his courtesan, which upsets Gaston. He is disturbed by Gigi's knowledge of society gossip. After presenting her with an expensive emerald bracelet, he grows increasingly uncomfortable with the unrelenting scrutiny being heaped on them. Honoré congratulates Gaston on his new courtesan and remarks that Gigi is so delightful that she will likely keep him amused for months.
Gaston is so disgusted by his uncle's remark, he drags Gigi from the restaurant all the way back home without saying a word while she cries and protests, not understanding what is wrong. After returning Gigi home in tears, he wanders the dark streets of Paris in silence, only to finally return and asks Madame Alvarez for Gigi's hand in marriage.
The final sequence returns to Honoré Lachaille, who proudly points out Gaston and Gigi getting into a carriage in the Bois de Boulogne: elegant, beautiful, and happily married.
