Dogs in the Wizarding World

Dogs are a common animal in both the Muggle and Wizarding world, where they appear as mundane pets, formidable magical guards, and significant magical forms. They are featured as the Animagus form of a key character, a common form for the Patronus Charm, and the physical manifestation of a dark omen. Both ordinary and magical dogs play various roles throughout the Harry Potter series, from providing companionship to guarding powerful magical objects.

• Fang: Rubeus Hagrid's large Boarhound. Despite his intimidating size, Fang is described as being a “bloody coward.” He is a loyal companion to Hagrid and friendly towards Harry Potter, Ron Weasley, and Hermione Granger. Fang accompanies Harry and Draco Malfoy into the Forbidden Forest during their detention and is present for many significant events at Hagrid's Hut.
• Fluffy: A giant, monstrous three-headed dog bred by Rubeus Hagrid. Albus Dumbledore used Fluffy to guard the trapdoor leading to the underground chambers protecting the Philosopher's Stone. The only known way to subdue Fluffy is to play him music, which causes him to fall asleep. After the threat to the Stone was over, Hagrid set Fluffy free in the Forbidden Forest. (Pottermore)
• Ripper: Marjorie Dursley's vicious bulldog. Ripper is one of her twelve bulldogs and her favourite. He travels with her to Number 4, Privet Drive, where he exhibits aggressive behaviour, notably chasing Harry Potter up a tree.
• The Grim: A spectral omen of death that takes the form of a giant, ghostly black dog with flaming eyes. In their third year, Professor Trelawney identifies what she believes to be the Grim in Harry Potter's tea leaves, causing widespread alarm. Sightings of the Grim were actually sightings of Sirius Black in his Animagus form.
• Sirius Black's Animagus Form: Often mistaken for the Grim, Sirius Black's unregistered Animagus form is a large, shaggy black dog, which earned him the Marauder nickname Padfoot. This form was instrumental in his escape from Azkaban and allowed him to move about undetected, watch Harry Potter's Quidditch matches, and communicate with his friends.

The most prominent example of a dog Animagus is Sirius Black, who transforms into a large black dog. This non-verbal, wandless magic allowed him to slip past the Dementors of Azkaban, as they could not sense his less complex canine emotions.

The dog is a known form for a corporeal Patronus.

• Ron Weasley's Patronus takes the form of a Jack Russell Terrier. He successfully casts it to drive away Dementors during the Battle of Hogwarts. He also uses it as a messenger to communicate with Harry at Number 12, Grimmauld Place.
• An unnamed member of the Order of the Phoenix sends a dog-shaped Patronus to The Burrow to warn guests at Bill Weasley and Fleur Delacour's wedding that the Ministry of Magic had fallen and that Rufus Scrimgeour was dead.

• In the film adaptations of the Harry Potter series, Fang was portrayed by a Neapolitan Mastiff. (film)
• J.K. Rowling has stated that she chose a Jack Russell Terrier for Ron Weasley's Patronus because she herself owns a Jack Russell, and it is a breed known for chasing otters, a subtle reference to Hermione Granger's otter Patronus. (J.K. Rowling interview)