Webster's Dictionary refers to the line of dictionaries first developed by Noah Webster in the early 19th century, and also to numerous unrelated dictionaries that added Webster's name just to share his prestige. The term is a genericized trademark in the U.S.A. for comprehensive dictionaries of the English language^{[citation needed]}.

Noah Webster (1758–1843), the author of the readers and spelling books that dominated the American market at the time, spent decades of research in compiling his dictionaries. His first dictionary, A Compendious Dictionary of the English Language, appeared in 1806. In it, he introduced features that would be a hallmark of future editions such as American spellings (center rather than centre, honor rather than honour, program rather than programme, etc.) and included technical terms from the arts and sciences rather than confining his dictionary to literary words. He spent the next two decades working to expand his dictionary.

In 1828, at the age of 70, Noah Webster published his American Dictionary of the English Language (ADEL) in two quarto volumes containing 70,000 entries, as against the 58,000 of any previous dictionary. There were only 2,500 copies printed, at $20 for the two volumes. Partially due to the relatively high price, the book sold poorly and all copies were not bound up at the same time; the book also appeared in publisher's boards; other original bindings of a later date are not unknown.