Winnie-the-Pooh is a 1926 children's book by English author A. A. Milne and English illustrator E. H. Shepard. The book is set in the fictional Hundred Acre Wood, with a collection of short stories following the adventures of an anthropomorphic teddy bear, Winnie-the-Pooh, and his friends Christopher Robin, Piglet, Eeyore, Owl, Rabbit, Kanga, and Roo. It is the first of two story collections by Milne about Winnie-the-Pooh, the second being The House at Pooh Corner (1928). Milne and Shepard collaborated previously for English humour magazine Punch, and in 1924 created When We Were Very Young, a poetry collection. Among the characters in the poetry book was a teddy bear Shepard modelled after his son's toy. Following this, Shepard encouraged Milne to write about his son Christopher Robin Milne's toys, and so they became the inspiration for the characters in Winnie-the-Pooh.

The book was published on 14 October 1926, and was both well-received by critics and a commercial success, selling 150,000 copies before the end of the year. Critical analysis of the book has held that it represents a rural Arcadia, separated from real-world issues or problems, and is without purposeful subtext. More recently, criticism has been levelled at the lack of positive female characters (i.e. that the only female character, Kanga, is depicted as a bad mother).

Winnie-the-Pooh has been translated into over fifty languages; a 1958 Latin translation, Winnie ille Pu, was the first foreign-language book to be featured on the New York Times Best Seller List, and the only book in Latin ever to have been featured. The stories and characters in the book have been adapted in other media, most notably into a franchise by The Walt Disney Company, beginning with Winnie the Pooh and the Honey Tree, released on 4 February 1966 as a double feature with The Ugly Dachshund. It remains protected under copyright in other countries, including the UK.

Before writing Winnie-the-Pooh, A. A. Milne was already a successful writer. He wrote for English humour magazine Punch, had published a mystery novel, The Red House Mystery (1922), and was a playwright. Milne began writing poetry for children after being asked by fellow Punch contributor, Rose Fyleman. Milne compiled his first verses for publishing, and though his publishers were initially hesitant to publish children's poetry, the poetry collection When We Were Very Young (1924) was a success. The illustrations were done by artist and fellow Punch staff E. H. Shepard.

Among the characters in When We Were Very Young was a teddy bear that Shepard modelled after one belonging to his son. With the book's success, Shepard encouraged Milne to write stories about Milne's young son, Christopher Robin Milne, and his stuffed toys. Among Christopher's toys was a teddy bear he called "Winnie-the-Pooh". Christopher got the name "Winnie" from a bear at the London Zoo, Winnipeg. "Pooh" was the name of a swan in When We Were Very Young. Milne used Christopher and his toys as inspiration for a series of short stories, which were compiled and published as Winnie-the-Pooh. The model for Pooh remained the bear belonging to Shepard's son.

Winnie-the-Pooh was published on 14 October 1926 by Methuen & Co. in England and E. P. Dutton in the United States. As a work first published in 1926, the book entered the public domain in the United States on 1 January 2022. British copyright of the text expires on 1 January 2027 (70 calendar years after Milne's death) while British copyright of the illustrations expires on 1 January 2047 (70 calendar years after Shepard's death).

Some of the stories in Winnie-the-Pooh were adapted by Milne from previous published writings in Punch, St. Nicholas Magazine, Vanity Fair and other periodicals. The first chapter, for instance, was adapted from "The Wrong Sort of Bees", a story published in the London Evening News in its issue for Christmas Eve 1925. Classics scholar Ross Kilpatrick contended in 1998 that Milne adapted the first chapter from "Teddy Bear's Bee Tree", published in 1912 in Babes in the Woods by Charles G. D. Roberts.

The stories in the book can be read independently. The plots do not carry over between stories (with the exception of Stories 9 and 10).