The Devil's Dictionary is a satirical dictionary written by American journalist Ambrose Bierce, consisting of common words followed by humorous and satirical definitions. The lexicon was written over three decades as a series of installments for magazines and newspapers. Bierce's witty definitions were imitated and plagiarized for years before he gathered them into books, first as The Cynic's Word Book in 1906 and then in a more complete version as The Devil's Dictionary in 1911.

Initial reception of the book versions was mixed. In the decades following, however, the stature of The Devil's Dictionary grew. It has been widely quoted, frequently translated, and often imitated, earning a global reputation. In the 1970s, The Devil's Dictionary was named as one of "The 100 Greatest Masterpieces of American Literature" by the American Revolution Bicentennial Administration. It has been called "howlingly funny", and Wall Street Journal columnist Jason Zweig said in an interview that The Devil's Dictionary is "probably the most brilliant work of satire written in America. And maybe one of the greatest in all of world literature."

Prior to Bierce, the best-known writer of amusing definitions was Samuel Johnson. His A Dictionary of the English Language was published 15 April 1755. Johnson's Dictionary defined 42,733 words, almost all seriously. A small handful have witty definitions and became widely quoted, but they were infrequent exceptions to Johnson's learned and serious explanations of word meanings.

Noah Webster earned fame for his 1806 A Compendious Dictionary of the English Language and his 1828 An American Dictionary of the English Language. Most people assume that Webster's text is unrelieved by humor, but (as Bierce himself was to discover and describe), Webster made witty comments in a tiny number of definitions.

Gustave Flaubert wrote notes for the Dictionary of Received Ideas (sometimes called Dictionary of Accepted Ideas; in French, Le Dictionnaire des idées reçues) between 1850 and 1855 but never completed it. Decades after his death, researchers combed through Flaubert's papers and published the Dictionary under his name in 1913 (two years after Bierce's book The Devil's Dictionary), "But the alphabetful of definitions we have here is compiled from a mass of notes, duplicates and variants that were never even sorted, much less proportioned and polished by the author."

Bierce took decades to write his lexicon of satirical definitions. He warmed up by including definitions infrequently in satirical essays, most often in his weekly columns "The Town Crier" or "Prattle". His earliest known definition was published in 1867.

His first try at a multiple-definition essay was titled "Webster Revised". It included definitions of four terms and was published in early 1869. Bierce also wrote definitions in his personal letters. For example, in one letter he defined "missionaries" as those "who, in their zeal to lay about them, do not scruple to seize any weapon that they can lay their hands on; they would grab a crucifix to beat a dog."

By summer of 1869 he had conceived of the idea of something more substantial: "Could any one but an American humorist ever have conceived the idea of a Comic Dictionary" he wrote.