The third and definitive film adaptation of L. Frank Baum's 1900 children's fantasy, this musical adventure is a genuine family classic that made Judy Garland a star for her heartfelt performance as Dorothy Gale, an orphaned young girl unhappy with her drab black-and-white existence on her aunt and uncle's dusty Kansas farm. Dorothy yearns to travel "over the rainbow" to a different world, and she gets her wish when a tornado whisks her and her little dog, Toto, to the Technicolorful land of Oz. Having offended the Wicked Witch of the West (Margaret Hamilton), Dorothy is protected from the old crone's wrath by the ruby slippers that she wears. At the suggestion of Glinda, the Good Witch of the North (Billie Burke), Dorothy heads down the Yellow Brick Road to the Emerald City, where dwells the all-powerful Wizard of Oz, who might be able to help the girl return to Kansas. En route, she befriends a Scarecrow (Ray Bolger), a Tin Man (Jack Haley), and a Cowardly Lion (Bert Lahr). The Scarecrow would like to have some brains, the Tin Man craves a heart, and the Lion wants to attain courage; hoping that the Wizard will help them too, they join Dorothy on her odyssey to the Emerald City.

Garland was MGM's second choice for Dorothy after Shirley Temple dropped out of the project; and Bolger was to have played the Tin Man but talked co-star Buddy Ebsen into switching roles. When Ebsen proved allergic to the chemicals used in his silver makeup, he was replaced by Haley. Gale Sondergaard was originally to have played the Wicked Witch of the West in a glamorous fashion, until the decision was made to opt for belligerent ugliness, and the Wizard was written for W.C. Fields, who reportedly turned it down because MGM couldn't meet his price. Although Victor Fleming, who also directed Gone With the Wind, was given sole directorial credit, several directors were involved in the shooting, included King Vidor, who shot the opening and closing black-and-white sequences. Harold Arlen and E.Y. Harburg's now-classic Oscar-winning song "Over the Rainbow" was nearly chopped from the picture after the first preview because it "slowed down the action." The Wizard of Oz was too expensive to post a large profit upon initial release; however, after a disappointing reissue in 1955, it was sold to network television, where its annual showings made it a classic.