Argus Filch

Argus Filch is the caretaker of Hogwarts School of Witchcraft and Wizardry. He is a Squib, a non-magical person born to at least one wizarding parent, a fact that has left him deeply bitter and resentful towards the student body. Known for his foul temper, his deep affection for his cat Mrs. Norris, and his constant, fruitless war against the poltergeist Peeves, Filch serves as a minor antagonist and disciplinarian throughout the series. He patrols the castle's corridors obsessively, always hoping to catch students breaking rules so he can lobby for the return of corporal punishment.

Much of Filch's life before his employment at Hogwarts is unknown, though his status as a Squib meant he was unable to attend the school as a student. At some point, he was hired as the castle's caretaker, a position he holds for the entirety of the series. His daily life at Hogwarts consists of patrolling corridors with Mrs. Norris, cleaning up messes left by students and Peeves, and complaining to Albus Dumbledore about the need for harsher punishments. His office contains a large collection of confiscated magical joke items and a filing cabinet meticulously detailing the transgressions of countless students, with Fred Weasley and George Weasley being his primary targets. In Harry Potter's second year, Mrs. Norris becomes the first victim of the Petrification by the Basilisk from the Chamber of Secrets. A devastated Filch initially blames Harry. Later that year, Harry discovers a letter in Filch's office for a Kwikspell correspondence course, revealing Filch's secret shame of being a Squib. Filch's desire for cruel discipline finds a champion in Dolores Umbridge during Harry's fifth year. He becomes her most enthusiastic supporter, eagerly posting her many Educational Decrees and gleefully accepting her permission to use corporal punishment on students. He is the only staff member, besides Umbridge herself, who is genuinely sad to see her forced out of the school. During the Battle of Hogwarts, Filch is present within the castle. He is initially seen complaining that students are out of bed during the evacuation, but he ultimately participates in the school's defence in a non-combatant role, helping to retrieve the injured and clear rubble.

Filch is described as a stooped, rheumy-eyed man with thinning grey hair and a rasping voice. He often wears a dusty brown coat and shuffles as he walks, his face frequently twisted into an expression of suspicion or fury. His personality is defined by bitterness and resentment. He despises the students of Hogwarts, jealous of the magical ability he lacks. He is quick to anger, vindictive, and derives immense pleasure from the idea of punishing students. His only real source of affection is his cat, Mrs. Norris, for whom he cares deeply. He is sycophantic towards figures of authority who grant him power, such as Dolores Umbridge, but is generally unpleasant to everyone else. His eternal, losing battle with Peeves underscores his constant state of frustration.

As a Squib, Argus Filch possesses no personal magical abilities. His attempt to learn basic magic through a Kwikspell course proved unsuccessful, a source of great embarrassment for him. Despite his lack of magic, Filch possesses an unparalleled and encyclopedic knowledge of Hogwarts Castle's secret passages, hidden corridors, and shortcuts. This knowledge makes him an exceptionally effective, if unpleasant, caretaker, allowing him to appear seemingly out of nowhere to catch students breaking rules. His familiarity with the castle's secrets is said to be rivaled only by those who possess the Marauder's Map.

• Mrs. Norris: His scrawny, dust-coloured cat and constant companion. She acts as his deputy, patrolling the castle corridors and alerting Filch with an almost psychic connection whenever a student is misbehaving.
• Chains and Manacles: Filch keeps a set of manacles and chains polished and ready in his office, fantasizing about the day the old punishments are reinstated at Hogwarts.
• Kwikspell Course: A set of introductory magical lessons for witches and wizards with little talent. Harry discovers the envelope for this course in Filch's office.
• Confiscated Items: His office is filled with items he has taken from students over the years, including enchanted objects like Fanged Frisbees.

• Mrs. Norris: Filch's primary and perhaps only meaningful relationship is with his cat. He talks to her as if she were human and is utterly distraught when she is petrified, demonstrating a capacity for affection he shows to no one else.
• Peeves: The poltergeist is Filch's nemesis. Their ongoing war is a staple of Hogwarts life, with Filch constantly cleaning up the chaos Peeves creates and unsuccessfully begging the Headmaster to have him expelled.
• Fred Weasley and George Weasley: The Weasley twins are Filch's greatest adversaries among the student body. They are responsible for a vast number of the infractions recorded in his filing cabinets, and he holds a special hatred for them.
• Harry Potter: Filch dislikes Harry intensely, viewing him as just another rule-breaking, messy student. He frequently tries to get Harry into trouble, from his first year until his last.
• Albus Dumbledore: As his employer, Filch is subservient to Dumbledore but often complains to him. Dumbledore tolerates Filch's unpleasantness, likely out of a sense of responsibility and pity for his condition as a Squib in a magical world.
• Dolores Umbridge: Filch is her most loyal ally on the Hogwarts staff. He adores her authoritarian methods and is overjoyed when she grants him permission to whip students, a power he had long craved.

• Argus: In Greek mythology, Argus Panoptes was a giant with one hundred eyes who served as a watchman for the goddess Hera. This is a fitting name for Hogwarts's ever-watchful, spying caretaker.
• Filch: A verb meaning “to steal something of little value.” This reflects his petty nature and his role in confiscating items from students.

• In the film adaptations, Argus Filch is portrayed by actor David Bradley.
• The films omit the subplot revealing that Filch is a Squib. The scene where Harry Potter discovers the Kwikspell letter in his office is not included, leaving his lack of magical ability implied rather than explicitly stated.
• J.K. Rowling has stated that the connection between Filch and Mrs. Norris is not magical. Mrs. Norris is simply a very intelligent and unpleasant cat who has a strong bond with her equally unpleasant owner (Pottermore).