Lyman Frank Baum (May 15, 1856 – May 6, 1919) was an American author of children's books, best known for writing The Wonderful Wizard of Oz. He wrote thirteen novel sequels, nine other fantasy novels, and a host of other works (55 novels in total, plus four "lost" novels, 83 short stories, over 200 poems, an unknown number of scripts, and many miscellaneous writings), and made numerous attempts to bring his works to the stage and screen. His works anticipated such century-later commonplaces as television, augmented reality, laptop computers (The Master Key), wireless telephones (Tik-Tok of Oz), women in high risk, action-heavy occupations (Mary Louise in the Country), and the ubiquity of advertising on clothing (Aunt Jane's Nieces at Work).

Baum was born in Chittenango, New York, in 1856, into a devout Methodist family. He had German, Scots-Irish, and English ancestry, and was the seventh of nine children born to Cynthia Ann (née Stanton) and Benjamin Ward Baum, only five of whom survived into adulthood. He was named "Lyman" after his father's brother, but always disliked this name, and preferred to go by his middle name, "Frank". His mother, Cynthia Stanton, was a direct descendant of Thomas Stanton, one of the four Founders of what is now Stonington, Connecticut.

Benjamin Baum was a wealthy German American businessman, originally a barrel maker, who had made his fortune in the oil fields of Pennsylvania. Baum grew up on his parents' expansive estate, Rose Lawn, which he always remembered fondly as a sort of paradise. As a young child, he was tutored at home with his siblings, but at the age of 12, he was sent to study at Peekskill Military Academy. He was a sickly child given to daydreaming, and his parents may have thought he needed toughening up. But after two utterly miserable years at the military academy, he was allowed to return home. Frank Joslyn Baum, in his biography, To Please a Child, claimed that this was following an incident described as a heart attack, though there is no contemporary evidence of this (and much evidence that material in Frank J.'s biography was fabricated).

Baum started writing at an early age, perhaps due to an early fascination with printing. His father bought him a cheap printing press; which, with the help of his younger brother Henry (Harry) Clay Baum, with whom he had always been close, he used to produce The Rose Lawn Home Journal. The brothers published several issues of the journal, which included advertisements, perhaps which they may have sold. Rose Lawn was located in Mattydale, New York. The house burned down in the 1950s, and is now the site of an abandoned skating rink. The only remains of Rose Lawn are a few concrete steps, located behind the building. By the time he was 17, Baum established a second amateur journal, The Stamp Collector, printed an 11-page pamphlet called Baum's Complete Stamp Dealers' Directory, and started a stamp dealership with friends.

At the age of 20, Baum took on a new vocation: the breeding of fancy poultry, a national craze at the time. He specialized in raising a particular breed of fowl, the Hamburg. In March 1880 he established a monthly trade journal, The Poultry Record, and in 1886, when Baum was 30 years old, his first book was published: The Book of the Hamburgs: A Brief Treatise upon the Mating, Rearing, and Management of the Different Varieties of Hamburgs.

Despite financial difficulties, Frank was always the spotlight of fun around the household. Due to the fact that one of his trades was selling fireworks, he always made the Fourth of July memorable. His skyrockets, Roman candles, and fireworks filled the sky, while many people around the neighborhood would gather in front of the house to watch the displays. Christmas was even more festive. Frank played Santa for the family. While his father placed the Christmas tree in the front parlor behind closed drapes, Frank would decorate the tree and talk to them from behind the drapes, although they never could manage to see him. He kept up this tradition all his life.

At about the same time, Baum embarked upon his lifetime infatuation with the theater, a devotion which would repeatedly lead him to failure and near-bankruptcy. His first such failure occurred when a local theatrical company duped him into replenishing their stock of costumes, with the promise of leading roles that never came his way. Disillusioned, Baum left the theatre — temporarily — and went to work as a clerk in his brother-in-law's dry goods company in Syracuse. At one point, he found another clerk locked in a store room dead, an apparent suicide. This incident appears to have inspired his locked room story, "The Suicide of Kiaros", first published in the literary journal, The White Elephant.

Yet Baum could never stay away from the stage long. He continued to take roles in plays, performing under the stage names of Louis F. Baum and George Brooks.

In 1880, his father built him a theatre in Richburg, New York, and Baum set about writing plays and gathering a company to act in them. The Maid of Arran, a melodrama with songs based on William Black's novel A Princess of Thule, proved a modest success. Baum not only wrote the play but composed songs for it (making it a prototypical musical, as its songs relate to the narrative), and acted in the leading role. His aunt, Katharine Gray, played his character's aunt. She was the founder of Syracuse Oratory School, and Baum advertised his services in her catalog to teach theatre, including stage business, playwriting, directing, and translating (French, German, and Italian), revision, and operettas, though he was not employed to do so. On November 9, 1882, Baum married Maud Gage, a daughter of Matilda Joslyn Gage, a famous women's suffrage and radical feminist activist. While Baum was touring with The Maid of Arran, the theatre in Richburg caught fire during a production of Baum's ironically-titled parlor drama, Matches, destroying not only the theatre, but the only known copies of many of Baum's scripts, including Matches, as well as costumes.

In July 1888, Baum and his wife moved to Aberdeen, Dakota Territory, where he opened a store, "Baum's Bazaar". His habit of giving out wares on credit led to the eventual bankrupting of the store, so Baum turned to editing a local newspaper, The Aberdeen Saturday Pioneer, where he wrote a column, Our Landlady.

After Baum's newspaper failed in 1891, he, Maud and their four sons moved to Humboldt Park section of Chicago, where Baum took a job reporting for the Evening Post. Beginning in 1897, for several years he edited a magazine for advertising agencies focused on window displays in stores. The major department stores created elaborate Christmas time fantasies, using clockwork mechanisms that made people and animals appear to move. In 1900, Baum published a book about window displays in which he stressed the importance of mannequins in drawing customers. He also had to work as a traveling salesman.

In 1897, he wrote and published Mother Goose in Prose, a collection of Mother Goose rhymes written as prose stories, and illustrated by Maxfield Parrish. Mother Goose was a moderate success, and allowed Baum to quit his door-to-door sales job (which had had a negative impact on his health). In 1899 Baum partnered with illustrator W. W. Denslow, to publish Father Goose, His Book, a collection of nonsense poetry. The book was a success, becoming the best-selling children's book of the year.

In 1914, having moved to Hollywood years earlier, Baum started his own film production company, The Oz Film Manufacturing Company, which came as an outgrowth of the Uplifters. He served as its president, and principal producer and screenwriter. The rest of the board consisted of Louis F. Gottschalk, Harry Marston Haldeman, and Clarence R. Rundel. The films were directed by J. Farrell MacDonald, with casts that included Violet MacMillan, Vivian Reed, Mildred Harris, Juanita Hansen, Pierre Couderc, Mai Welles, Louise Emmons, J. Charles Haydon, and early appearances by Harold Lloyd and Hal Roach. Silent film actor Richard Rosson appeared in one of the films, whose younger brother Harold Rosson photographed The Wizard of Oz (1939). After little success probing the unrealized children's film market, Baum came clean about who wrote The Last Egyptian and made a film of it (portions of which are included in Decasia), but the Oz name had, for the time being, become box office poison and even a name change to Dramatic Feature Films and transfer of ownership to Frank Joslyn Baum did not help. Unlike with The Fairylogue and Radio-Plays, Baum invested none of his own money in the venture, but the stress probably took its toll on his health.

On May 5, 1919, Baum suffered from a stroke. He died quietly the next day, nine days short of his 63rd birthday. At the end he mumbled in his sleep, then said, "Now we can cross the Shifting Sands." He was buried in Glendale's Forest Lawn Memorial Park Cemetery. His final Oz book, Glinda of Oz, was published on July 10, 1920, a year after his death. The Oz series was continued long after his death by other authors, notably Ruth Plumly Thompson, who wrote an additional nineteen Oz books.