An author who doesn't want their authorship known will use a PenName. An author who wants everyone to know they don't want their authorship known will use Anonymous, or a pen name that very obviously presents itself as a pen name.

This is done to convey the impression -- which may even be true -- that the author would be in trouble were his or her identity known. So it's often done with controversial works, or works that wish to present themselves as such, and with exposes.

Compare PenName and AlanSmithee. Contrast SameFaceDifferentName, where the pseudonym may not even be particularly opaque and serves largely to emphasize GenreAdultery.

!!Examples:
* ''TheWotch'' by Anne Onymous.
* ''Film/PrimaryColors'' by Anonymous. Fifteen years later, ''{{O}}'' by Anonymous.
** Also by Anonymous ''Literature/TheBookWithNoName''.
* A Prussian nobleman wrote plays under the name J.E. Mand -- ''jemand'' is German for "someone."
* ''Literature/GoAskAlice''... [[BasedOnAGreatBigLie allegedly]].
* ''TheBrideStrippedBare''. Australian Nikki Gemmell eventually revealed her authorship.
* ''Literature/TheNameOfThisBookIsSecret'' and its sequels by PseudonymousBosch, although it's pretty much confirmed by now that he's author Raphael Simon.
* ''Literature/{{Frankenstein}}'', on its initial publication, to hide that the author was a young woman.
* During her lifetime, Creator/JaneAusten's novels only identified the author with the words "By a Lady".
** Parodying this, TheTwoRonnies serial 'The Phantom Raspberry Blower of Old London Town' was credited to 'Spike Milligan & A Gentleman' (The Gentleman being Ronnie Barker).
%%* ''DeathNote'' and ''{{Bakuman}}'' by Tsugami Ohba/I don't know Japanese -- language or culture -- and can't tell if the pseudonym presents itself as such in some way
* Nearly all creators of the VisualNovel KatawaShoujo use nicknames (e.g. cpl_crud, silentcook, Aura)
* Many of the credits in Mega Man II are aliases, e.g. Inafking, Tom Pon, 2m03cm Man, Yuukichan's Papa, Fish Man)
* MarvelComics:
** ''Brotherhood'', about [[ComicBook/{{X-Men}} the Brotherhood of Evil Mutants]], was apparently written by "X". Popular opinion has it that this was Howard Mackie, but the truth has never been revealed.
** ''The Generic Comic Book'' is credited to "An Author, a Pecilist, an Inker, a Colorist and a Letterist."
* The ''Federalist Papers'' was published under with the pseudonym "Publius". The papers were drafted in response to the ''Anti-Federalist Papers'', a series of parallel essays, published under the pseudonyms "Cato", "Brutus", "Centinel", and "Federal Farmer".
* WebOriginal/VoxAndKingBeau is a Creepypasta originally posted on /x/ that takes the format of a young woman named Vox who posts on /x/ looking for advice. The author of the story never goes by anything other than Vox or hints to the story being fictional at all.
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