Parseltongue was the language of serpents (as well as other magical serpentine creatures, like the Runespoor and Basilisk) and those who could converse with them. A wizard or witch who could speak Parseltongue was known as a Parselmouth. It was a very uncommon skill, and was known to be an almost exclusively hereditary trait. Not counting Herpo the Foul, who predated him by several centuries, nearly all known Parselmouths were descended from Salazar Slytherin, with Harry Potter being a notable exception (although he gained his ability as a Parselmouth in an unorthodox manner).
- "And the second man’s voice changed. He started making noises such as Frank had never heard before; he was hissing and spitting without drawing breath. Frank thought he must be having some sort of fit or seizure."
- — The Muggle Frank Bryce overhearing Lord Voldemort speak in Parselmouth in the Riddle House[src]
Parseltongue was, when spoken, a hissing sound, similar to that of a snake; as such, normal people could not understand it (one known exception being Dumbledore). Apart from merely communicating with serpentine lifeforms, Parselmouths also seemed to be able to influence the will of serpents to a certain extent. Aside from serpent-based creatures, Parselmouths could communicate with each other with the language, as Harry understood Tom Riddle's commands to the Serpent of Slytherin, and the House of Gaunt communicated with each other almost exclusively in Parseltongue. Though the ability was hereditary, not all of those with it could speak it themselves. Isolt Sayre was able to understand the Horned Serpent she visited but not communicate with it herself.
The ability to actually speak Parseltongue — not just imitate it as Ron Weasley did — was considered an attribute of a Dark Wizard, which was partly due to the fact that both Salazar Slytherin and Lord Voldemort possessed this ability. Another notable Dark Wizard who was also a Parselmouth was Herpo the Foul. However, as Albus Dumbledore pointed out, there were Parselmouths among the great and good as well, the most well-known of which was Harry Potter. Paracelsus, a notable alchemist and a "medical genius", was credited with the discovery of Parseltongue in the sixteenth century, despite the existence of speakers like Herpo the Foul or Salazar Slytherin in the classical and medieval ages. Because of the uncommonness of Parselmouths, Voldemort came to believe it made him special.
An unknown member of the Dark Force Defence League once stated when asked regarding the matter by Rita Skeeter — "Personally, I would be highly suspicious of anybody who could converse with snakes, as serpents are often used in the worst kinds of Dark Magic, and are historically associated with evildoers."
Harry Potter as a Parselmouth
Lord Voldemort passed the ability to speak and understand Parseltongue on to Harry Potter when he attacked him in infancy in 1981, inadvertently and unknowingly making him into a Horcrux. Harry first experienced conversation with snakes at age ten when he was taken to the zoo with his cousin Dudley Dursley and found himself communicating with a snake while in the reptile exhibit. Harry inadvertently caused the glass of the snake's tank to vanish, enabling it to escape.
Harry was not consciously aware of his ability to speak Parseltongue until 1992 after he was pitted against Draco Malfoy in the Duelling Club. Draco conjured a snake to attack him and, when the serpent turned its attention to Justin Finch-Fletchley, Harry was able to communicate with it to tell it not to attack. Harry's ability, so closely associated with Salazar Slytherin, caused hysteria among his fellow students because Writing on the Walls of Hogwarts Castle had foretold that the Heir of Slytherin would open the Chamber of Secrets, unleashing a monster that would attack the school's Muggle-born students. Even Severus Snape, who was previously enjoying Harry's horror at the snake, became horrified himself when he learned of Harry's ability.
The incident spread rumours that Harry may be the Heir and even Hermione Granger, one of Harry's best friends, acknowledged that there was a possibility that he was descended from Slytherin, as the Chamber had first been created 1000 years ago and its creator's bloodline over that time wasn't fully known. It was also at this time that he realized that he was speaking another language as Hermione and Ron couldn't understand what he was saying. 
The Heir of Slytherin was, in fact, Voldemort- a piece of his spirit contained within his diary that had possessed Ginny Weasley and forced her to commit the acts around the school. However, Harry was able to gain access to the Chamber by speaking the password in Parseltongue, and subsequently destroyed both the Basilisk within and the Diary. It was shortly after this incident that Harry learned how he acquired the ability.
When the wizarding world discovered Harry's ability to speak Parseltongue, courtesy of Rita Skeeter, people began to doubt his word, as Cornelius Fudge refused to believe Harry's claim of Voldemort's rebirth, partially due to being prejudicial toward Harry's ability to speak the language.
Harry also used his skill in Parseltongue to open Slytherin's Locket. When Harry, Ron Weasley, and Hermione Granger returned to Hogwarts to search for Ravenclaw's Diadem, Ron managed a weak imitation of the phrase Harry had spoken, to re-open the Chamber of Secrets so that he and Hermione could fetch the Basilisk's fangs, which Hermione used to destroy Hufflepuff's Cup.
Over the next twenty-two years, he never attempted to speak the language, presuming that it had died with Voldemort. However, in 2020, Harry discovered that he still had the ability, or had somehow regained it, despite his previous assumptions. While initially reluctant to speak the language, at Hermione's insistence Harry successfully spoke Parseltongue to open Delphini's enchanted room while searching for his missing son, Albus Potter. Later, Harry again used Parseltongue in order to impersonate the Dark Witch's father.
- Harry Potter
- Salazar Slytherin
- Tom Riddle
- Merope Riddle
- Marvolo Gaunt
- Morfin Gaunt
- Corvinus Gaunt
- Gormlaith Gaunt
- Herpo the Foul
Unconfirmed potential Parselmouths
The ability to speak Parseltongue being known to be hereditary, the blood relatives of known Parselmouths were potentially Parselmouths themselves.
Other instances of Parseltongue
People who were not Parselmouths but were able to speak or understand Parseltongue through various means:
- Ginny Weasley was able to speak Parseltongue while she was possessed by Tom Riddle's Diary, which enabled her to open the Chamber of Secrets.
- Ron Weasley was also able to open the Chamber of Secrets during the Battle of Hogwarts by repeating a fragment of Parseltongue he had heard Harry Potter use to open Salazar Slytherin's Locket, though it took him several tries to make it work.
- Albus Dumbledore could understand Parseltongue and repeat sentences in it verbatim; he may have been able to speak it in full, although this is unconfirmed.
- Newt Scamander mentioned in his magnum opus, Fantastic Beasts and Where to Find Them, that information on Runespoors, three-headed snakes from Africa, is based on the “writings of Parselmouths who have kept and conversed with these serpents”. There are likely to be African Parselmouths completely unrelated to the Gaunts.
- Bathilda Bagshot's carcass spoke in Parseltongue while it was occupied by Nagini.
- Isolt Sayre, a direct descendant of Salazar Slytherin, was able to understand a Horned Serpent which she regularly visited but was not able to speak Parseltongue herself.
Behind the scenes
- J. K. Rowling has stated that she took the name Parselmouth from an "old word for someone who has a problem with the mouth, like a hare lip".
- When Harry Potter and Hermione Granger went to Godric's Hollow in 1997, Nagini (inside the corpse of Bathilda Bagshot) tells Harry to "Come!" from the next room in Parseltongue. In reaction, Hermione jumps and clutches Harry's arm, and the two of them obey the command. It is unknown how Hermione seemed to understand this command, though it could be that she did not hear it well, and merely followed Harry. She could also have been frightened by the hissing sound she heard and then followed Harry.
- In the Philosopher's Stone film, Harry converses with a Burmese python, rather than a Boa Constrictor.
- Whenever it was spoken in the films, Parseltongue went untranslated except for one scene in Harry Potter and the Deathly Hallows: Part 2 when Voldemort was speaking to Nagini, where it was given subtitles. It was also heard in English in the first film when Harry was talking in the zoo.
- In the films, Parseltongue is depicted as sounding like a sibilant-filled language with readily discernible phonemes created by Dr Francis Nolan (as listed in the credits for Harry Potter and the Deathly Hallows). In the novels, it is only ever described as a low hissing noise, easily missed by non-Parselmouths — a far cry from the rather loud versions from the films.
- In the last two films, as Harry draws near a Horcrux he can hear, in addition to a whining noise, a faint voice which seems to speak in Parseltongue.
- It is possible that Parseltongue comes in variants for different languages, rather than being understood as the language spoken by the Parselmouth. The boa constrictor that Harry Potter converses with at the zoo uses the Portuguese word amigo rather than the English friend.
- The Parselmouth - provides an aural dictionary that offers visitors the chance to listen to translations of English words and phrases in Parseltongue
- Parseltongue translator (archived) - an official translator into Parseltongue.
- Parseltongue-inspired - Provides a hypothetical, written breakdown of Parseltongue in universe.
- Harry Potter and the Philosopher's Stone (First appearance)
- Harry Potter and the Philosopher's Stone (film)
- Harry Potter and the Chamber of Secrets (First identified as Parseltongue)
- Harry Potter and the Chamber of Secrets (film)
- Harry Potter and the Chamber of Secrets (video game)
- Harry Potter and the Goblet of Fire
- Harry Potter and the Goblet of Fire (film)
- Harry Potter and the Order of the Phoenix (film) (Heard in opening shot)
- Harry Potter and the Half-Blood Prince
- Harry Potter and the Half-Blood Prince (film)
- Harry Potter and the Deathly Hallows
- Harry Potter and the Deathly Hallows: Part 1
- Harry Potter and the Deathly Hallows: Part 2
- Harry Potter and the Cursed Child
- Harry Potter and the Cursed Child (play)
- Fantastic Beasts and Where to Find Them (Mentioned only)
- Wizarding World
- LEGO Harry Potter: Years 1-4
- LEGO Harry Potter: Years 5-7
- Harry Potter for Kinect
- Harry Potter: The Character Vault (Mentioned only)
Notes and references
- Harry Potter and the Chamber of Secrets, Chapter 11 (The Duelling Club)
- Fantastic Beasts and Where to Find Them
- Harry Potter and the Deathly Hallows, Chapter 35 (King's Cross)
- Harry Potter and the Goblet of Fire, Chapter 1 (The Riddle House)
- July 30, 2007 Bloomsbury Live Chat with J. K. Rowling
- Harry Potter and the Chamber of Secrets, Chapter 17 (The Heir of Slytherin)
- Harry Potter and the Half-Blood Prince, Chapter 10 (The House of Gaunt)
- Writing by J.K. Rowling: "Ilvermorny School of Witchcraft and Wizardry" at Wizarding World
- Harry Potter and the Goblet of Fire, Chapter 31 (The Third Task)
- Harry Potter and the Half-Blood Prince, Chapter 13 (The Secret Riddle)
- Harry Potter and the Philosopher's Stone (video game)
- Harry Potter and the Chamber of Secrets (video game)
- Harry Potter and the Philosopher's Stone, Chapter 2 (The Vanishing Glass)
- Harry Potter and the Chamber of Secrets, Chapter 9 (The Writing on the Wall)
- Harry Potter and the Goblet of Fire, Chapter 36 (The Parting of the Ways)
- Harry Potter and the Deathly Hallows, Chapter 19 (The Silver Doe)
- Harry Potter and the Deathly Hallows, Chapter 31 (The Battle of Hogwarts)
- Harry Potter and the Cursed Child
- Harry Potter and the Half-Blood Prince, Chapter 17 (A Sluggish Memory)
- Writing by J.K. Rowling: "Chamber of Secrets" at Wizarding World
- Harry Potter and the Deathly Hallows, Chapter 17 (Bathilda's Secret)
- 2003 Albert Hall Interview with J.K. Rowling at Accio Quote