"The Secret Life of Walter Mitty" (1939) is a short story by James Thurber. The most famous of Thurber's stories, it first appeared in The New Yorker on March 18, 1939, and was first collected in his book My World and Welcome to It (Harcourt, Brace and Company, 1942). It has since been reprinted in James Thurber: Writings and Drawings (The Library of America, 1996, ISBN 1-883011-22-1), is available on-line on the New Yorker website, and is one of the most frequently anthologized short stories in American literature. The story is considered one of Thurber's "acknowledged masterpieces". It was made into a 1947 movie of the same name, with Danny Kaye in the title role, though the movie is very different from the original story. It was also adapted into a 2013 film, which is again very different from the original.
The name Walter Mitty and the derivative word "Mittyesque" have entered the English language, denoting an ineffectual person who spends more time in heroic daydreams than paying attention to the real world, or more seriously, one who intentionally attempts to mislead or convince others that he is something that he is not.
The story had an influence on other humorists, notably Mad founder Harvey Kurtzman (who borrowed the story's sound effects), playwright George Axelrod (who employed Mitty-like fantasies in The Seven Year Itch) and animation director Chuck Jones (who created a Mitty-like child character for Warner Bros. cartoons).
When referencing actor Errol Flynn, Warner Brothers studio head Jack L. Warner noted in his autobiography, My First Hundred Years in Hollywood, "To the Walter Mittys of the world he [Flynn] was all the heroes in one magnificent, sexy, animal package".