Ozma of Oz, published on July 29, 1907, was the third book of L. Frank Baum's Oz series. It was the first in which Baum was clearly intending a series of Oz books. Where at the end of The Wonderful Wizard of Oz, Dorothy's silver shoes were lost in the desert, at the end of Ozma of Oz, Glinda tells her the magic belt she could wish herself home with would likewise be lost, and Dorothy carefully gives it to Ozma, in order that she might go home but the magic still be preserved, and they arrange that Ozma will use it to wish Dorothy back to Oz at need.
It is also the first book where the majority of the action takes place outside of the Land of Oz. Only the final two chapters take place in Oz itself. This reflects a subtle change in theme: in the first book, Oz is the dangerous land through which Dorothy must win her way back to Kansas; in the third, Oz is the end and aim of the book. Dorothy's desire to return home is not as desperate as in the first book, and it is her uncle's need for her rather than hers for him that makes her return.
It was illustrated throughout in color by artist John R. Neill.
The book bore the following dedication: "To all the boys and girls who read my stories — and especially to the Dorothys — this book is lovingly dedicated."
Uncle Henry has been ordered by his doctor to take a vacation from his Kansas farm to Australia. He and his niece Dorothy Gale are aboard a steamship traveling there when they are caught in a fierce storm and separated. Dorothy is blown overboard along with a yellow hen from her uncle's farm that was on the ship.
Dorothy and Billina the hen wash ashore and pick something to eat from a lunch-pail tree. Dorothy guesses that they are in a "fairy country" because lunch pails do not normally grow on trees and animals like Billina do not talk, but it's not Oz because that country has no seashore. They come across a message inscribed in the sand: "BEWARE THE WHEELERS"! Soon the pair meets these gaudily dressed, loud-yelling creatures who have wheels instead of hands and feet, and roll around on all fours. Dorothy and Billina climb a rocky mountain to escape the Wheelers and find a door carved into its side. Having found the key by the door, they open it and find Tik-Tok, a round copper mechanical man whom they activate with the key like a wind-up toy.
Tik-Tok tells Dorothy and Billina about the land of Ev where they are now and the loss of its royal family to the magic of the Nome King. He takes them to safety from the Wheelers to the royal residence, where the head-exchanging Princess Langwidere, the niece of the deceased king of Ev, locks Dorothy and Billina in a high tower. Tik-Tok stops once in mid-motion, and he will not be able to move again until he is wound up with the key.
Ozma and her companions (many of whom appeared in the two previous Oz books) cross the Deadly Desert with the aid of a magic carpet provided by Glinda to free the royal family of Ev, and Ozma has Dorothy released from Langwidere's custody. Cheerful reunions are had by the Scarecrow, the Tin Woodman, and the Cowardly Lion, and new introductions are made to Ozma and the Hungry Tiger, a massive tiger hamstrung by his conscience.
The expedition journeys to the underground kingdom of the Nomes, where the Nome King reveals that he has turned the royal family into ornaments around his palace. The Oz people given the option to guess which ornaments they are (he doesn't reveal that they are royal purple ones), but if they fail, they will also become ornaments. Ozma, the twenty-seven soldiers of the Royal Army of Oz, the Tin Woodman, the Scarecrow, and Tik-Tok all suffer this fate (Dorothy escapes it only by touching a purple ornament in one of her guesses). When the guests from Oz retire one night, Billina learns which of the Nome King's ornaments were once people and about the magic belt which he wears.
Billina was originally not going to be allowed to guess, but she so infuriates the Nome King by laying an egg (poisonous to any Nome) under his throne that he lets her guess. And all of hers turn out to be right, thanks to Billina's previous night of overhearing the Nome King's transforming conventions. The Nome King commands his army to recapture all of them by force, but Dorothy takes the Magic Belt, the Army's sole private takes the offensive, and Billina's eggs are left in the Nomes' paths so they do not dare follow.
After returning the royal family of Ev (the queen mother, five boys, and five girls) to their rightful place, Ozma, Dorothy, and the others return to Oz where a great victory celebration is held in the Emerald City. Dorothy is officially made a Princess of Oz, Billina elects to remain in Oz, and Ozma uses the Magic Belt to send Dorothy to Australia to be reunited with Uncle Henry.
Elements from Ozma of Oz and the previous novel, The Marvelous Land of Oz, were incorporated into the 1985 film Return to Oz, featuring Fairuza Balk as Dorothy. Although most of the plot was taken from Ozma, the action was chiefly re-located to the derelict Emerald City, ruled by Princess Mombi (Princess Langwidere in all but name) and her Wheelers. In the second half of the film, Dorothy, Billina, Tik-Tok, and other new friends traveled to the Nome King's mountain, to rescue the Scarecrow from the King's ornament collection, which were emerald green unlike the books royal purple. The 1939 film's famous ruby slippers were used in place of the Magic Belt.
The 1986 Japanese animated series Oz no Mahōtsukai included the story. It was later shortened and edited into a single feature for US video and DVD release.
The book was also made into a Canadian animated feature film in 1987 Dorothy Meets Ozma of Oz. It is a condensed version, running only 28 minutes. A video release features a live introduction by actor Michael Gross.