"Diary of a Madman" is short story by Russian author Creator/NikolaiGogol. [[ExactlyWhatItSaysOnTheTin It consists of entries from a madman]], the madman in this case being Poprishchin, a 40 year old titular counsellor who serves as an assistant to the director of his division, a job consisting mostly of sharpening quills. He entertains delusions of self-importance, holding great pride in being officially a nobleman. He has fallen in love with the director's daughter, and desires to be noticed by her.
One day, while walking to work, he encounters the director's carriage, carrying his daughter to the store. While observing, he hears a voice, which he discovers to be [[SpeaksFluentAnimal that of the dogs]]. The rest of the story details his descent into madness, told through the entries of his diary.
A planned AnimatedAdaptation in the 1970s never materialised, but the narration by Creator/KennethWilliams was later turned into a radio play by Creator/TheBBC.
Absolutely no relation to the 1963 Creator/VincentPrice horror film, or the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' fanfic ''Fanfic/DiariesOfAMadman''.
!!This story provides examples of:
* BedlamHouse: Poprishchin is eventually sent there, where he undergoes such wonderful therapies like being beaten with a stick or having cold water poured on him.
* ClassicalAntihero: Poprishchin's a complete failure in every regard.
* GlobalIgnorance: After going completely off the deep end, Poprishchin starts believing that Spain and China are one and the same.
* MoodWhiplash: Mostly funny. And then it ends with him sobbing in a heap.
* NapoleonDelusion: An early example-- [[spoiler: Poprishchin doesn't believe he's Napoleon, but he does think he's the King of Spain.]]
* RippedFromTheHeadlines: The crisis in Spain Poprishchin refers to appears to be the then-current [[https://en.wikipedia.org/wiki/First_Carlist_War First Carlist War]], a civil war waged over the legitimacy of the succession of Princess Isabella (who is indeed mentioned, but not by name) to the Spanish throne.
* SanitySlippage: The story details this, as Poprishchin's grip on reality continues to slip, eventually resulting in [[spoiler: him believing himself the heir to the Spanish throne.]]
* SmallNameBigEgo: Poprishchin, who thinks he is a person of some importance, when, well, he isn't.
* SpeaksFluentAnimal: Poprishchin's first delusion is that he can understand the talks of dogs, and later the letters they write each other.
* ThroughTheEyesOfMadness: It's the diary of a madman.