When Ron meets Harry on the Hogwarts Express in Harry Potter and the Philosopher's Stone, they have this conversation:

“What House are your brothers in?” asked Harry.

“Gryffindor,” said Ron. Gloom seemed to be settling on him again. “Mum and Dad were in it, too. I don’t know what they’ll say if I’m not. I don’t suppose Ravenclaw would be too bad, but imagine if they put me in Slytherin.”

“That’s the House Vol-, I mean, You-Know-Who was in?”

“Yeah,” said Ron. He flopped back into his seat, looking depressed.
- Harry Potter and the Philosopher’s Stone, Chapter 6 (The Journey from Platform Nine and Three-Quarters)

So Ron apparently knows Voldemort was in Slytherin. But at the end of Harry Potter and the Chamber of Secrets, it is made clear that Voldemort's real identity as the brilliant (Slytherin) student Tom Riddle is unknown to most - in Dumbledore's own words:

‘Very few people know that Lord Voldemort was once called Tom Riddle. I taught him myself, fifty years ago, at Hogwarts. He disappeared after leaving the school … travelled far and wide … sank so deeply into the Dark Arts, consorted with the very worst of our kind, underwent so many dangerous, magical transformations, that when he resurfaced as Lord Voldemort, he was barely recognisable. Hardly anyone connected Lord Voldemort with the clever, handsome boy who was once Head Boy here.’
- Harry Potter and the Chamber of Secrets, Chapter 18 (Dobby’s Reward)

So how could Ron (as well as, I guess, most wizards) not know Voldemort's real identity yet know the actual House he was in at Hogwarts?

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    "Hardly anyone": Some people recognised who he was and given that the house he was in is likely better food for the rumour mill than that he was some student the latter probably fell to the floor.
    – TheLethalCarrot
    Commented Apr 30, 2018 at 15:21
  • 50
    @Kevin - Because Hagrid told him - "‘Better Hufflepuff than Slytherin,’ said Hagrid darkly. ‘There’s not a single witch or wizard who went bad who wasn’t in Slytherin. You-Know-Who was one.’"
    – Valorum
    Commented Apr 30, 2018 at 18:01
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    @Kevin - Hagrid was at Hogwarts at the same time as Riddle. Being that Hagrid is extremely close to and trusted by Dumbledore, was an original member of the OotP, it stands to reason Hagrid would be among those who know
    – NKCampbell
    Commented Apr 30, 2018 at 18:32
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    Did Hagrid know that Tom Riddle was Voldemort?
    – Valorum
    Commented Apr 30, 2018 at 18:47
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    I don't know your real identity, how do I know you have a Stack Exchange account? Commented May 1, 2018 at 0:23

9 Answers 9


The Dark Lord himself might have said he was in Slytherin.

When the Dark Lord was at the height of his power, though he might not have wanted to talk much about his father or Muggle heritage, he was proud to be the descendant of Salazar Slytherin. He had been even as Tom Riddle, and though he wanted to be rid of his father’s name, he was quite proud of his relation to Slytherin. He called himself "Lord Voldemort, heir of Salazar Slytherin", indicating that he intended to keep the Slytherin connection even after he became Lord Voldemort.

“Now, Harry, I’m going to teach you a little lesson. Let’s match the powers of Lord Voldemort, heir of Salazar Slytherin, against famous Harry Potter, and the best weapons Dumbledore can give him.”
- Harry Potter and the Chamber of Secrets, Chapter 17 (The Heir of Slytherin)

He carried this pride into adulthood as well. When he takes over Hogwarts many years later, he announced that there will be no more houses, only Slytherin.

“There will be no more Sorting at Hogwarts School,’ said Voldemort. ‘There will be no more houses. The emblem, shield and colours of my noble ancestor, Salazar Slytherin, will suffice for everyone, won’t they, Neville Longbottom?”
- Harry Potter and the Deathly Hallows, Chapter 36 (The Flaw in the Plan)

It didn’t seem like the Dark Lord was trying to keep his Hogwarts house secret. Even if he didn’t want the wizarding world knowing that he was once Tom Riddle, he was likely perfectly happy to say he was a Slytherin.

Him saying it himself would explain why people seem so certain about his house, rather than it being treated like a widely believed rumor (like the circumstances of his disappearance, or Harry being thought to be the heir of Slytherin by his classmates). His claim to be the heir of Slytherin and ability to speak Parseltongue would help support the idea he was in Slytherin to anyone who knew of them, but the simplest way that people could seem to know his house is for him to have said it.

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    This make sense, although it seems a little unlikely that he would say he was in Slytherin House, rather than that he was the heir of Slytherin.
    – Buzz
    Commented May 1, 2018 at 1:54
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    It didn’t seem like the Dark Lord was trying to keep his Hogwarts house secret. Even if he didn’t want the wizarding world knowing that he was once Tom Riddle, he was likely perfectly happy to say he was a Slytherin. Agree. He was proud of his status. He makes it clear in CoS too that he wanted to finish the work. And didn't he say that the colour of Slytherin will be the only colour (i.e. only Slytherin has a place) in the future - when he and everyone else (but Harry and Narcissa of course!) thought Harry was dead? Ah yes you actually cited that!
    – Pryftan
    Commented May 1, 2018 at 2:32
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    @Pryftan Thanks! :) He was quite proud of his status, so I doubt he’d hide being a Slytherin. He‘d have no reason to hide it. He mentions being the heir of Salazar Slytherin, so he could easily have mentioned that he was in Slytherin house as well. If he did, the rest of the wizarding world would likely presume it was true and not bother to question it, despite not knowing who he used to be. That the Dark Lord wanted to make it the only house in Hogwarts and abolish all others shows he’d have to be proud of the house specifically, in addition to his connection to Salazar Slytherin.
    – Obsidia
    Commented May 2, 2018 at 17:41
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    @bertieb You’re welcome! Okay, I’ve changed it for you. Sorry for accidentally giving you spoilers - I wasn’t trying to spoil anyone. I’ll be honest though, I prefer it without the tags, since now I’ve hidden what I consider my best point. Hopefully you enjoy the rest of the series!
    – Obsidia
    Commented May 3, 2018 at 18:07
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    @bertieb Thanks! :) You’re welcome - hopefully you won’t see any spoilers until then! When you get to the fifth book you’ll see where my name’s from. ;)
    – Obsidia
    Commented May 3, 2018 at 20:31

I don't think we can exclude the possibility that Ron - and more-or-less everyone, actually - simply assumed that he was in Slytherin. It obviously has a reputation for generating villains. Recall this statement:

"‘Better Hufflepuff than Slytherin,’ said Hagrid darkly. ‘There’s not a single witch or wizard who went bad who wasn’t in Slytherin. You-Know-Who was one.’"

Harry Potter and the Philosopher's Stone

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    Hagrid seems fairly certain that the Dark Lord was actually a Slytherin - in fact he’s the first one that Hagrid cites as an evil Slytherin. It seems unlikely that he’d choose someone who everyone just guessed was in Slytherin (if there wasn’t some sort of evidence) as his first example of a bad Slytherin. In addition, he stated it pretty definitively - “You-Know-Who was one” rather than “everyone says You-Know-Who was one”.
    – Obsidia
    Commented May 1, 2018 at 0:19
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    @Bellatrix: Hagrid might not be the most careful scholar. I don't think his definitive statement is very strong evidence that it's known fact rather than widely believed. (Not disputing the fact, just the use of Hagrid's phrasing as evidence. Your answer that this info was Voldy's own statements is the most likely, IMO.) Commented May 1, 2018 at 1:21
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    @PeterCordes But the thing is his relationship with Dumbledore. Yes he was biased against Slytherin but I suspect that in this case he had a reason to say Voldemort was Slytherin; that doesn't mean his statement cited here is true but then again he might be rather sore about being expelled by Riddle who he would have known to be Slytherin (and of course Dumbledore suspected Riddle but knew he couldn't do much in the matter with Dippet or anyone else for that matter).
    – Pryftan
    Commented May 1, 2018 at 1:35
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    Why would everyone assume he was at Hogwarts at all when there are other wizarding schools? Hagrid is an exception since he could have learned this from Dumbledore. It's one thing to see Voldemort proudly declare he is the heir of Slytherin but quite a separate issue to assume he was ever at Hogwarts at all before that information was more widely publicised. So I don't get why "more-or-less everyone would assume this.
    – syntonicC
    Commented May 1, 2018 at 12:52
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    Hagrid also knew Tom Riddle when he studied at Hogwarts. He is clearly more informed than most.
    – TGar
    Commented May 1, 2018 at 14:50

Voldemort was indeed a known Parselmouth

Tom Riddle was a half-blood. The Riddle name did not belong to a known pureblood family. Therefore, Voldemort needed to show that he was great in some way, in order to convince witches and wizards to follow him.

After graduating from Hogwarts and disassociating himself from the Riddle name, he could have publicly flaunted his ability to speak in Parseltongue. This would serve as proof that Voldemort was descended from Salazar Slytherin himself, and provide credibility to his image as the champion of pure-bloods, as Salazar Slytherin was also popularly believed to have hated muggleborns due to the legend of Slytherin's monster being created to purge muggleborns from Hogwarts.

“It matters,” said Hermione, speaking at last in a hushed voice, “because being able to talk to snakes was what Salazar Slytherin was famous for. That’s why the symbol of Slytherin House is a serpent.”

-Hermione Granger, Harry Potter and the Chamber of Secrets

Therefore, Ron and the entire wizarding world must have taken Voldemort's status as a Parselmouth as proof that he was descended from Salazar Slytherin.

Parseltongue, the ability to converse with snakes, has long been considered a Dark Art. Indeed, the most famous Parselmouth of our times is none other than You-Know-Who himself.

-The Daily Prophet

Harry Potter and the Goblet of Fire, Page 612

This particular quote proves that Voldemort was a known Parselmouth.

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    Is it common knowledge that Parselmouths are direct descendants of the Slytherin bloodline? Commented May 1, 2018 at 21:54
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    @Slytherincess It may not be common knowledge, but even then, most witches and wizards are prone to jumping to conclusions. The fact that Salazar Slytherin was a world-famous parselmouth helped Voldemort build credibility on his ancestry.
    – Simpleton
    Commented May 2, 2018 at 4:05
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    Wait. The snake symbol for Slytherin wasn't because his name was Slytherin? Commented May 2, 2018 at 23:40
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    @Quasi_Stomach Little-known fact: the Muggle word 'slither' is derived from Salazar Slytherin's name. Commented May 3, 2018 at 0:14

The Dark Mark

When Voldemort was in power, there were attacks everywhere, and when Death Eaters attack somewhere they cast the Dark Mark, which is Voldemort’s symbol with a snake on it. I think people could make deductions about his house afterwards.

There is citation somewhere in the books about the Dark Mark being seen very frequently at Voldemort’s golden years. If someone finds and edits this answer , It will be a more complete answer.


Dumbledore may have been correct that few people knew Voldemort's identity during his reign of Terror and even afterward. However, the British wizarding community is too small for it to have been kept a secret in retrospect. With only a few thousand individuals, it would be relatively straightforward to track down everyone who were still living or confirmed dead after the dark lord's defeat. Voldemort would have to be among those unaccounted for.

Most wizards seemed to want to know as little as possible about Voldemort after his passing. However, a curious individual like Arthur Weasley (who also had access to Ministry of Magic population records) ought to have been able to work it out. He presumably shared the information about what house Voldemort had been in with his family, but out of some misplaced sense of propriety did not reveal Voldemort's original name.

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    The problem is how would Arthur know Voldemort's real name? He was surprised iirc at the end of Chamber of Secrets to find it out. You're right though that he certainly did look into things, was curious and was against Voldemort in both wars. Some wizards would take the not wanting to know anything about Voldemort to the extreme esp after Harry and Dumbledore insisted he had returned.
    – Pryftan
    Commented May 1, 2018 at 1:38
  • Snape knew Voldemort's real identity. So did Peter Pettigrew. Snape likely would have told Dumbledore when he came over to the good side and Dumbledore would likely have shared that info with the Order. Commented May 1, 2018 at 23:02

Arthur and Molly Weasley were in the original Order of the Phoenix. Assuming Dumbledore told the Order that Voldemort was previously known as Tom Riddle (in a know-your-enemy discussion), then it is reasonable to assume that all the Weasley children knew as well, especially after a dozen years of Voldemort's absence.

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    The assumption is I believe wrong though. Dumbledore wouldn't have had a reason to tell them and I believe they were alarmed to find out that Ginny was possessed by Voldemort that is Tom Riddle!
    – Pryftan
    Commented May 1, 2018 at 1:39
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    @Pryftan Mr. and Mrs. Weasley were alarmed and horrified to learn their daughter was in mortal peril. I don't think their alarm went as far as learning the secret identity of the perpetrator. In either case, a quote to back up our assertions would be nice...
    – scott
    Commented May 1, 2018 at 15:16
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    Absolutely not. Ginny doesn't know, or she wouldn't have trusted that magic diary. Neither does Ron, when they find the diary he remembers the name... only because he had to clean his trophy many times due to an 'accident'. It is funny in retrospect how You-Know-Who's trophy was the one that suffered this fate, though. There's no reason to think that their brothers knew his identity, and probably not even their parents knew it.
    – Ángel
    Commented May 1, 2018 at 20:26
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    Well since you asked: He had so far avoided mentioning Riddle’s diary — or Ginny. She was standing with her head against Mrs. Weasley’s shoulder, and tears were still coursing silently down her cheeks.[...] Then: 'What interests me most,' said Dumbledore gently, 'is how Lord Voldemort managed to enchant Ginny, when my sources tell me he is currently in hiding in the forests of Albania.' Finally: 'W-what’s that? said Mr. Weasley in a stunned voice. 'You- Know-Who? En-enchant Ginny? But Ginny’s not . . . Ginny hasn’t been . . . has she?'
    – Pryftan
    Commented May 1, 2018 at 22:12
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    @scott Yes, T.M. Riddle was engraved on the front of the diary. “Hang on,’ said Ron, who had approached cautiously and was looking over Harry’s shoulder. ‘I know that name … T. M. Riddle got an award for special services to the school fifty years ago.” - Harry Potter and the Chamber of Secrets, Chapter 13 (The Very Secret Diary) Ron connected it with a trophy, not the Dark Lord. In addition, Tom introduced himself to Harry as Tom Riddle. ‘Hello, Harry Potter. My name is Tom Riddle. How did you come by my diary?” - Harry Potter and the Chamber of Secrets, Chapter 13 (The Very Secret Diary)
    – Obsidia
    Commented May 2, 2018 at 23:51

Possibly Voldemort issued a proclamation that mentioned that he was the natural leader of all (or all British?) wizards and gave some justifications for that, possibly including a claim that he had once been the top student in Slytherin, the house that the greatest wizards all came from and the house whose members were the rightful leaders of the wizards.

Thus everyone would know that Voldemort was a former Slytherin student who would have graduated sometime in the previous century or so (since it might be somewhat rare for wizards to live more than about a century after graduating about age 18), without knowing which former Slytherin student it was.

  • Ah but the question is: did he? There isn't any canon to suggest he did at this point. What there is though is that he surprised everyone by working at Borgin and Burkes (such a bright student choosing that? But it was a conscious choice with a purpose); then of course Miss Smith was found dead, Hokey had been given a false memory and Riddle disappeared - along with two artefacts. He would resurface years later hardly recognisable after all his transformations. He did later on suggest this though but not until Deathly Hallows. So yes..but no.
    – Pryftan
    Commented May 12, 2018 at 3:38
  • One other thing just crossed my mind that would (ever so slightly) improve your answer (though it depends on if you're answering from the 2000s or the time frame of the story itself) - technically his demise was in 1998 which was last century but the way I interpret your second paragraph is everyone are those who were alive and in the wizarding world at the time - last century - which means that it should be this century. Maybe 'past century'? Just some thoughts that probably don't matter all that much - but FWIW there they are.
    – Pryftan
    Commented Jul 27, 2018 at 22:01
  • @Pyftan I have changed my answer to make the chronological meaning clearer. Commented Sep 4, 2018 at 3:51
  • Fair enough. I honestly can't remember what it was all about and I have far too much going on to really consider it more. Ah, right. Maybe you were referring to my second comment. Yes. I see that now. Better indeed.
    – Pryftan
    Commented Sep 7, 2018 at 0:15

Inferred, from Death Eaters' ties to Slytherin House

The majority of confirmed(1) and suspected(2) Death Eaters seem to have been former students of Slytherin House, and some came from the most proudly aristocratic levels of magical British society. These people saw their privileges as rightful, they were determined to increase their power, and they spent their Hogwarts years networking with other Slytherins of similar mind(3). Whether or not such a collection of ambitious traditionalist bigots was capable of rallying for years around a non-Slytherin leader, the general magical public would have inferred that the Death Eaters could only follow a leader who came from Slytherin.

(1) IE, those who were convicted (such as the escapees from Azkaban in the 1997 mass breakout) or pardoned (Snape).

(2) EG, Lucius Malfoy.

(3) EG, Tom Riddle's core group.


There's always the "Lee Jordan argument": if all signs point to Slytherin then it's Slytherin. As formulated in Chapter Fourteen of Chamber of Secrets:

"That's two Gryffindors down, not counting a Gryffindor ghost, one Ravenclaw, and one Hufflepuff," said the Weasley twins' friend Lee Jordan, counting on his fingers. "Haven't any of the teachers noticed that the Slytherins are all safe? Isn't it obvious all this stuff's coming from Slytherin? The Heir of Slytherin, the monster of Slytherin – why don't they just chuck all the Slytherins out?" he roared, to nods and scattered applause.

Similarly, when it comes to Voldemort's house the signs point to Slytherin:

  • Virtually all the Death Eaters were from Slytherin.

  • Slytherin was known as the house that produced Dark wizards.

  • Voldemort and the Death Eaters aligned with Slytherin views about blood purity and Muggle inferiority.

  • The Dark Mark's symbol was a serpent, just like Slytherin's symbol.

Of course, it's also possible that someone who knew spread the word.

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