Non-fiction (or nonfiction) is the form of any narrative, account, or other communicative work whose assertions and descriptions are understood to be factual. This presentation may be accurate or not—that is, it can give either a true or a false account of the subject in question—however, it is generally assumed that authors of such accounts believe them to be truthful at the time of their composition or, at least, pose them to their audience as historically or empirically true. Note that reporting the beliefs of others in a non-fiction format is not necessarily an endorsement of the ultimate veracity of those beliefs, it is simply saying it is true that people believe them (for such topics as mythology, religion). Non-fiction can also be written about fiction, giving information about these other works.

Non-fiction is one of the two main divisions in writing, particularly used in libraries, the other form being fiction. However, non-fiction need not be written text necessarily, since pictures and film can also purport to present a factual account of a subject.