The idea-expression divide is a concept in copyright law which states that copyright does not protect ideas, information or function, but only the form of expression of ideas. Only the way in which something has been expressed is protectable by copyright.

In the English decision of Donoghue v. Allied Newspapers Ltd [1938] Ch 106, the court said that "the person who has clothed the idea in form, whether by means of a picture, a play or a book" owns the copyright. Even more eloquently, Latham CJ in the Australian decision of Victoria Park Racing and Recreation Grounds Co. Ltd v. Taylor (1937) 58 CLR 479 and 498 said that if you are the first person to announce that a man has fallen off a bus, you cannot use the law of copyright to stop other people from announcing that fact.