Gigi (French pronunciation: is a 1958 American musical-romance film directed by Vincente Minnelli and processed using Metro-Goldwyn-Mayer's color film process Metrocolor. The screenplay by Alan Jay Lerner is based on the 1944 novella of the same name by Colette. The film features songs with lyrics by Lerner and music by Frederick Loewe, arranged and conducted by André Previn.

In 1991, Gigi was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant". The American Film Institute ranked it #35 in AFI's 100 Years...100 Passions. The film is considered the last great Metro-Goldwyn-Mayer musical and the final great achievement of the Freed Unit, headed by producer Arthur Freed, although he would go on to produce several more films, including the musical Bells Are Ringing in 1960.

Set in La Belle Époque of the turn-of-the-19th-cum-20th century Paris, the film opens with Honoré Lachaille (Maurice Chevalier) surrounded by members of high society in the Bois de Boulogne. As a charming old roué, he remarks that in Paris, marriage is not the only option for wealthy young bon vivants like his nephew Gaston (Louis Jourdan), who is bored with life. The one thing Gaston truly enjoys is spending time with Madame Alvarez (Hermione Gingold), whom he calls Mamita, and especially her granddaughter, the precocious, carefree Gilberte, also called Gigi (Leslie Caron).

Following the "family tradition", Madame Alvarez sends Gigi to her great aunt Alicia (Isabel Jeans) to be groomed as a courtesan, a dignified word for a mistress of a wealthy man, to learn etiquette and charm. To Alicia, love is an art and a necessary accomplishment for Gigi's social and economic future, but Gigi disdains the trivial love that a man and his mistress share. Remaining true to her girlish yet charming personality, she finds herself having the most fun when she is with Gaston, whom she regards as an older brother.

Like his uncle, Gaston is known as a wealthy womanizer. The whole of Paris watches his every move, and Parisian high society shows unrestrained judgment towards his mistresses and him. Gaston's latest mistress attempts to run off with her ice skating instructor. In response, Gaston publicly humiliates her, resulting in her attempted suicide. After this affair, Gaston plans to retreat to the country, but his uncle insists on his staying in Paris and attending more parties.

Gigi makes a wager during a card game with Gaston that if he loses, he must take her grandmother and her to the seaside with him when he goes on vacation. Gaston agrees, loses, and the three travel to Trouville. Gaston and Gigi spend their hours having fun together, and Honoré and Madame Alvarez reminisce about their once-passionate affair. While other women at the resort are shown holding perfect poise and giving off an air of boredom and disdain for anything unfamiliar, Gigi pulls Gaston out of his depressive rut with her carefree attitude.

Once Gigi and her grandmother return to Paris, Gaston goes to Monte Carlo. During this time, Gigi's aunt and grandmother discuss the possibility of Gigi becoming Gaston's mistress, thereby fulfilling their plans for her. Madame Alvarez, though dubious at first, agrees to let Gigi train around the clock to prepare for Gaston's return. Gigi accepts this as a necessary evil.

When Gaston returns, he is surprised and discomfited when Gigi appears in her new, adult dress. Gaston tells her that she looks like a giraffe, and that he misses her old costumes. He storms out, then realizes his folly and rushes back to apologize. He tells Gigi that she looks lovely and says that he will prove it to her by taking her to tea at the Reservoir. Gigi's grandmother refuses and tells Gaston that it may ruin her reputation to be seen unchaperoned with Gaston before her reputation has even begun. Gaston, angered, storms out once again.

As Gaston walks, he reflects about Gigi. He realizes that Gigi has become a woman whose charm and wit have set his head spinning. He concludes that he has developed a romantic desire for Gigi. Although he hesitates on account of their age difference, he also realizes that he loves her even more than he thought (unheard of between a man and his mistress) and he wants to be with her. He proposes an arrangement to Madame Alvarez and Aunt Alicia for Gigi to become his mistress. They are overjoyed; Gigi is not.

Gaston talks to Gigi and she tells him that she is not the type of girl who wants celebrity only to be abandoned by him one day, and then becoming someone else's mistress. Gigi wants their relationship to remain platonic, but when Gaston accidentally reveals that he loves Gigi, she bursts into tears, upset that he would want to expose her to the uncertainty of being his mistress if he actually loves her. Gaston leaves angered. He later runs into Honoré, who declares that Gigi's family has always been a bit odd. Gigi sends Gaston a message asking him to come and talk to her. When he arrives, she admits that she would rather be miserable with him than miserable without him. She agrees to accompany him in public. Gaston buys an expensive piece of jewelry for Gigi and later, when he arrives for their date, he finds Gigi dressed in her finery and is entranced by her beauty.

The couple go to Maxim's restaurant, where Gigi acts the role of a courtesan perfectly. Gaston is upset seeing Gigi demonstrate the knowledge of a courtesan, and, after giving her the gift, becomes even more concerned for Gigi because of the unrelenting attention and judgment by the other patrons. Honoré delivers a crushing blow when he congratulates Gaston on his new courtesan, and makes disparaging remarks about Gigi. Gaston, too much in love with Gigi to give her this appalling life of uncertainty and social judgment, makes her leave without a word and drags her up the stairs to her apartment. He walks away, but soon stops a little way down the street and realizes the depth of his love for her. He returns to her apartment and proposes marriage.

The final sequence returns to Honoré Lachaille, proudly pointing out Gaston and Gigi getting into their carriage in the Bois de Boulogne: the couple is elegant, beautiful, and happily married.