!!Nearly Headless Nick (Creator/JohnCleese)
[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/Nick_6278.png]]
The resident ghost of Gryffindor House. Known in life as Sir Nicholas de Mimsy-Porpington, he was beheaded (well, nearly) on Halloween in the year 1492. As per JacobMarleyApparel, he is now stuck spending eternity with his head just barely connected to his body by a thin strip of flesh. This makes him ineligible for the Headless Hunt, much to his chagrin.

Nick is occasionally proud and pompous, but is nevertheless always a friendly mentor to young Gryffindors. He appears in all the books, but in only the first two movies.

* ChuckCunninghamSyndrome: Only in the movies, in which he disappeared after the second film.
* HeadlessHorseman: He wants to be one, but the fact that his head isn't completely detached makes this impossible.
* HiddenDepths: Nick is very philosophical about the nature and condition of being a ghost and how cowardly it is and what a poor option it is to the unexplained wizarding afterlife.
* HollywoodCostuming: Wears a ruff (useful for hiding his severed neck) despite dying a good fifty years before the ruff was commonly worn.
* NegateYourOwnSacrifice: Isn't killed by the basilisk's gaze due to already being dead.
* OffWithHisHead: Well, not quite all the way off.
* OnlyKnownByTheirNickname: He prefers to be known as "Sir Nicholas".
* TorsoWithAView
* WhatCouldHaveBeen: J.K. Rowling's website includes a song explaining how he died, which was cut from the second book. (Long story short: a noblewoman hired him to fix her teeth. [[MagicMisfire He accidentally gave her tusks]]. She wasn't happy.)

!!Moaning Myrtle (ShirleyHenderson)
[[quoteright:321:http://static.tvtropes.org/pmwiki/pub/images/Myrtle_9604.png]]
The ghost of a Muggle-born girl who attended Hogwarts at the same time as Tom Riddle and Rubeus Hagrid. She was murdered by Riddle, via the basilisk, and he used her death to create the diary Horcrux. After spending some time haunting the AlphaBitch who tormented her when she was alive, the Ministry of Magic forced Myrtle to go haunt the place of her death instead. This was the bathroom containing the entrance to the Chamber of Secrets and she has remained there ever since.

She is, as Hermione tactfully observes in the second movie, "[[{{Understatement}} a little sensitive]]". "A little sensitive" means that she is an insane LargeHam with a HairTriggerTemper. In Myrtle's mind, everyone is constantly making fun of her and talking about her behind her back. Of course, this behavior [[SelfFulfillingProphecy causes people to make fun of her and talk about her behind her back]]. She also develops a humorous crush on Harry, although he generally finds her annoying.

In the books, Myrtle appears in ''[[Literature/HarryPotterAndTheChamberOfSecrets Chamber of Secrets]]'', ''[[Literature/HarryPotterAndTheGobletOfFire Goblet of Fire]]'', and ''[[Literature/HarryPotterAndTheHalfBloodPrince Half-Blood Prince]]''. In the films, her appearance in ''[[Film/HarryPotterAndTheHalfBloodPrince Half-Blood Prince]]'' was removed.

* AbhorrentAdmirer: To Harry.
* AdaptationalAttractiveness: A lesser-known example. The one or two descriptions and chapter-lead pictures we get of Myrtle show she was fairly significantly overweight and "doughy", which fits in with all the bullying she received. Shirley Henderson, meanwhile, was depicted as being a little "round of face" and perhaps a bit "mousy"[[note]]Henderson's casting was likely part of the idea, to make Myrtle seem a bit "off" compared to the actual kids[[/note]], but not even remotely unattractive; her Myrtle is downright ''cute'' (if a little... well, [[CovertPervert see below]]) in certain scenes of movie-''Goblet''.
** Her voice is also nowhere near as abrasive as Myrtle's is described as being - in the books her namesake moans are a namesake because they're by turns ear-splitting and intensely depressing, and she's unpleasant to listen to in general, while in the movie her plaintive cries do little more than pluck at heartstrings.
** Granted, unlike some of the other examples in the franchise, this can work just as well - Myrtle wasn't being teased for being ''ugly'', she was being teased for being on the cusp of being very attractive despite not even putting a lot of effort into it, and the other girls likely felt intimidated by her. Movie-Myrtle probably would've been knocking the boys dead in a few years had she not had her life cut short.
* AllThereInTheManual: In life, Myrtle was a Ravenclaw.
* AlliterativeName
* BitchInSheepsClothing[=/=]BewareTheQuietOnes: When we first see her, she comes off as either a massive [[TheWoobie woobie]] or an astounding parody thereof, but when describing to Harry and Ron how she died, she reveals that she spent a good chunk of her time as a ghost tormenting her childhood bully for many, many years out of spite.
* ChekhovsGunman: She appears throughout the second book, but it's only near the end that Harry and Ron realize that [[spoiler:she's the girl the Heir of Slytherin killed fifty years before]].
* TheConfidant: In ''Half-Blood Prince'', she becomes one for, of all people, Draco Malfoy. It's hinted she may have switched her affections from Harry to Draco.
* CovertPervert: Shy and mousy as she is, she still has that hobby mentioned below.
* DawsonCasting: Being in her thirties both times she played the role, Shirley Henderson is the oldest person to play a Hogwarts student in any of the movies.
* DisproportionateRetribution: Okay, Olive Hornby was a bully, but did she really deserve Myrtle's ghost {{Gaslighting}} her all that time?
** Well, Myrtle may not have ended up a ghost if she hadn't [[spoiler:been in the Chamber of Secrets entrance bathroom]] crying as a result of Olive's bullying...
* HairTriggerTemper: Among her other neuroses and insecurities, she has an extremely short temper regarding them. She especially gets upset when she's feeling excluded.
* ThePeepingTom: A pastime of hers, as revealed in ''Goblet''.
* NerdGlasses
* NoodleIncident: Why, exactly, does she have so much vitriol against the living mermaid portrait in the prefects' bathroom?
* Really700YearsOld: Being a ghost, she has remained physically (well, metaphysically) a teenager for over fifty years.
* SitcomArchNemesis: For [[NoodleIncident some reason]], she ''really'' hates the living mermaid portrait in the prefects' bathroom.
* {{Wangst}}: PlayedForLaughs [[invoked]]
* WhosLaughingNow: See DisproportionateRetribution and BitchInSheepsClothing above.

!!Helena Ravenclaw, the Grey Lady (Creator/KellyMacdonald)
[[quoteright:250:http://static.tvtropes.org/pmwiki/pub/images/Helena_2764.png]]
The daughter of Rowena Ravenclaw herself. Jealous of her mother, Helena stole her mother's diadem and was subsequently killed by the man who would become the Bloody Baron. Centuries later, she was effectively manipulated by the charms of one Tom Riddle. She revealed the location of her mother's diadem to him and he turned it into a Horcrux.

* AllThereInTheManual: Prior to ''[[Literature/HarryPotterAndTheDeathlyHallows Deathly Hallows]]'', WordOfGod provided the only indication that she existed. She does have a cameo in the first book, but this was only identified by WordOfGod.
* BerserkButton: Mention of Tom Riddle using her mother's diadem as a Horcrux has her go from withdrawn yet dignified to screaming rage about how Voldemort defiled it with Dark magic.
* BrainyBrunette
* ColorCharacter
* GreenEyedMonster: She was jealous of her mother and stole the diadem because she wanted to make herself more important.
* TheOtherDarrin: In the first film, she was played by Nina Young in a ContinuityCameo. Although she didn't have a single line, her role in the first movie was still larger than her role in any of the books prior to ''Hallows''.
* RavenHairIvorySkin: Both the books and the film portray her with long dark hair and pale skin. Fitting as she is not only the patron ghost of Ravenclaw, but Rowena Ravenclaw's own daughter.
* ShrinkingViolet: She is rather reclusive, not talking much to people or other ghosts, and she was shown briefly spending time in empty classrooms taking notes. The only person she does speak with regularly is Luna.
* UnwittingPawn: Of Riddle/Voldemort.
* WhatCouldHaveBeen: For ''Deathly Hallows: Part 2'', the role was offered to KateWinslet, but her agent rejected it.
* WomanInWhite

!!The Bloody Baron (Terence Bayler)
[[quoteright:333:http://static.tvtropes.org/pmwiki/pub/images/Baron_8470.png]]
The resident ghost of Slytherin House. In life, he was infatuated with Helena Ravenclaw. Some time after Helena had run away with her mother's diadem, Rowena was dying and sent the baron to find her daughter. He found her, but killed her in the struggle to bring her back. [[MyGodWhatHaveIDone Realizing what he'd done]], he then killed himself. As per JacobMarleyApparel, he will spend eternity covered in blood, hence the nickname.

During the time frame of the series, he is regarded as cold and mysterious, even by the other ghosts. For some reason, he is the only individual, other than Dumbledore, who can control Peeves.

* AlliterativeName
* AscendedExtra: In the [[VideoGame/HarryPotter first PC game]], the Bloody Baron appears a couple times as a minor enemy whom you have to avoid. It's not a huge role, but it's still more interaction than Harry ever had with him in the canon.
* ChainedByFashion
* ContinuityCameo: His only appearance in the films is in a brief shot during the opening feast from the first movie. Not that he appeared much more than that in the books anyway.
* DrivenToSuicide
* MyGodWhatHaveIDone
* NoodleIncident: Why is Peeves so afraid of him?
* OnlyKnownByTheirNickname: His real name has never been revealed, even when his past was.

!!The Fat Friar (Simon Fisher-Becker)
[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/Friar_5548.png]]
The resident ghost of Hufflepuff House. He seems to be cheerful and comical in personality, but nothing else is known about him other than the fact that he was evidently a friar when he was alive. Well, it ''is'' HufflepuffHouse, after all.

* AlliterativeName
* BigFun
* GoodShepherd: A friar that cures diseases and always forgives Peeves.
* NoGoodDeedGoesUnpunished: See TooDumbToLive below.
* NoSuchThingAsWizardJesus: Well, since a wizard can be a friar, apparently.
* ThePollyanna: He believes in giving Peeves second chances. And third chances. And fourth chances. And so on.
* TooDumbToLive: He went around instantly curing diseases and pulling rabbits out of goblets during his days among the living in the medieval era. Even though he was a decent person, one has to wonder why he was expecting ''not'' to get executed.

!!Peeves the Poltergeist
A poltergeist who haunts Hogwarts, making mischief wherever he can. He's not considered a ghost by the "other" ghosts, but he's often classified as one for convenience. However, it's worth noting that Peeves is not white or transparent, but is rather solid-looking and often dressed in loudly-colored clothes. Rowling defines Peeves as "an indestructible spirit of chaos" and that he "came with the building."

Peeves has no agenda, no motivation, no goals other than to create as much chaos as possible because ItAmusedMe. He is rude, crude, fond of practical jokes, and takes orders from no one other than the Bloody Baron, though he also shows some respect to Dumbledore and the like-natured [[TricksterTwins Weasley Twins]]. Peeves and Filch are constantly at war with each other, a conflict Harry and his friends generally do not involve themselves in.

Although Peeves has a sizable role in all the books and some of the video games, he never appears in the movies.

* AdaptedOut: From the movies.
* ArchEnemy: To Argus Filch.
* EvenEvilHasStandards: While Peeves is very much a troublemaker, he takes his pranking UpToEleven during ''[[Literature/HarryPotterAndTheOrderOfThePhoenix Order of the Phoenix]]'', wreaking complete havoc during Umbridge's reign. During DH, he causes havoc among the Death Eaters, and [[CrossesTheLineTwice composes a rude song to commemorate the defeat of Voldemort.]]
* FallingChandelierOfDoom: In one of his most famous scenes, he tried to cause this during his attacks against Umbridge. [[spoiler:[=McGonagall=] tells him he is unscrewing it improperly.]]
* GodzillaThreshold: When McGonagall summons ''Peeves'' for help, you '''know''' this is the final battle.
* GoldFishPoopGang: His role in the video games.
* HiddenDepths: He shows respect for Dumbledore and the Weasley twins, saluting the latter two when instructed to make Umbridge's life a living hell. He also actively fights for Hogwarts in the final battle with much gusto.
* ItAmusedMe: Pretty much the only reason he does anything.
* {{Jerkass}}: Half of his actions. Justified as he is the embodied entity of adolescent stress, adolescents tend to be jerkasses when stressed.
* {{Poltergeist}}: As revealed by [[AllThereInTheManual Pottermore]], he follows the definition of embodied entity of adolescent stress.
* OurSpiritsAreDifferent: Most notably in that Peeves is not a ghost exactly. He looks quite different and doesn't give any indication that he was ever "alive".
* TricksterArchetype: He loves tricking people with some ExactWords in his deal, like "Not saying nothing" unless Filch says "Please." Upon Filch saying "Please" Peeves replied "Nothing."
* {{Troll}}: ''Hoo boy''...Peeves loves chaos, and his every scene involves him pranking or causing trouble in some form. He never backs down from an opportunity to make fun of a student.
* WhatCouldHaveBeen: A scene with Rik Mayall of ''DropDeadFred'' fame as Peeves was shot for the first film, but was left on the cutting room floor and has never even been featured as a bonus feature on the [=DVDs=]. As is, Peeves never makes any appearances in the films.