Many stories use animals to symbolize a character's most important traits. This is also true of the Harry Potter series, where the animal form of a character's Patronus often symbolizes a character's defining traits or backstory. The Patronus Charm is a defensive spell that wizards and witches can use to protect themselves from Dementors. Patronuses can also be used to send messages to other wizards and witches.
It is a powerful, but difficult spell to master, and one that relies on the spellcaster focusing on a happy memory. Patronuses often take on the corporeal form of an animal, while some Patronuses are non-corporeal. Not all characters are capable of producing a Patronus, nor are all characters able to produce a corporeal Patronus. These are the Patronuses of the main characters in the Harry Potter series.
Remus Lupin: Wolf
Lupin's Patronus form isn't shown in the books or movies, and was originally shared on Pottermore in 2015. His Patronus is an ordinary wolf instead of a werewolf. The difference is that ordinary wolves can be family-orientated and non-aggressive.
Lupin still doesn't like his Patronus form, though, as it's a reminder of his werewolf condition. He purposely chooses to cast a non-corporeal Patronus instead, because of his discomfort with the wolf Patronus.
Minerva McGonagall: Cat
Minerva McGonagall is an Animagus who can transform into a cat. It is therefore fitting that McGonagall's Patronus matches her Animagus form. Much like a cat, McGonagall is a shrewd individual, and while she may have a stern disposition, she does have a tender side and cares deeply about others.
McGonagall uses her Patronus in the Harry Potter and the Deathly Hallows novel to tell the Heads of Houses that Hogwarts would soon be under attack by Voldemort and his followers.
Neville Longbottom: Non-Corporeal Patronus
Neville is one of the only main characters whose Patronus does not take on the form of an animal. He learns how to produce a non-corporeal Patronus along with many other members of Dumbledore's Army during their secret meetings in Harry Potter and the Order of the Phoenix.
The Patronus Charm is a powerful spell that can be difficult to master. Learning how to successfully cast a Patronus shows that Neville is capable of great things. It is one of the many steps he takes into becoming a leader and a more confident character.
Ginny Weasley: Horse
When practicing the Patronus Charm in the Harry Potter and the Order of the Phoenix film adaptation, Ginny's Patronus is shown to be a horse. This is not only true of the films, as it was also mentioned on Pottermore in 2016 that Ginny's Patronus is a horse.
When Harry first sees his stag Patronus, he thinks it is a horse. It is intriguing that his future wife's Patronus ended up being a horse instead. It is fitting that their Patronus forms are similar and that Harry is able to witness the first time Ginny produces the horse Patronus in the films.
Luna Lovegood: Hare
Luna is a joyful and free-spirited individual. It is only right that her Patronus takes on the joyful and free-spirited form of a hare. Like many other characters, she learns to cast a Patronus during a Dumbledore's Army meeting, but it's during the Battle of Hogwarts that her Patronus is particularly important.
When Harry, Ron, and Hermione are overcome with despair and unable to cast their Patronuses, Luna, Ernie Macmillan, and Seamus Finnegan are the ones who use their Patronuses to help repel a group of Dementors during the Battle of Hogwarts. Luna is also the one who helps Harry focus on something genuinely happy so he can conjure his powerful Patronus and cause the Dementors to scatter.
Severus Snape: Doe
Snape uses his doe Patronus to lead Harry toward the lake in the Forest of Dean where the Sword of Godric Gryffindor is hidden. It is seen again when Harry looks into Snape's memories and sees Snape conjure the Patronus in front of Dumbledore and utter the iconic "always" line.
Lily Potter's Patronus also took on the form of a doe. Snape's doe Patronus is a reminder of his unfulfilled love for Lily and that his deepest motivations are all about honoring her memory and finishing what she started.
Albus Dumbledore: Phoenix
Albus Dumbledore's Patronus form is first hinted at in Harry Potter and the Goblet of Fire when Harry sees what looks like a ghostly bird. J.K. Rowling confirmed fans' suspicions at the Edinburgh Book Festival in 2004 when she revealed that his Patronus takes on the form of a phoenix. In Harry Potter and the Deathly Hallows, Harry discounts Ron's theory about Dumbledore producing the doe Patronus that led to the Sword of Godric Gryffindor, as Harry knows Dumbledore has a phoenix Patronus.
Between Fawkes the phoenix, the Order of the Phoenix, and the significance of the phoenix seemingly confirming Credence to be a Dumbledore in Fantastic Beasts: The Crimes of Grindelwald, Albus Dumbledore has many connections that make it fitting for his Patronus to be a phoenix as well.
Ron Weasley: Jack Russell Terrier
In a 2005 interview, Rowling shared that she owns a Jack Russell dog, and that it's a sentimental choice on her part for it to also be the animal form of Ron's Patronus.
Jack Russell Terriers are also considered to be loyal and protective dogs, traits which are also true of Ron as an individual and in his relationships with his family, Harry, and Hermione.
Hermione Granger: Otter
Hermione's Patronus is an otter because otters are J.K. Rowling's favorite animal, and the animal Rowling would choose to be if she were an Animagus. Hermione masters the Patronus Charm during a Dumbledore's Army meeting in Harry Potter and the Order of the Phoenix.
Otters often symbolize friendship and kindness. Hermione has emphasized to Harry that she values traits like friendship and bravery even more than cleverness. She has always been a true friend to Harry and Ron and is one of the kindest characters in the series, all of which make an otter a worthy form for her Patronus.
Harry Potter: Stag
Harry's Patronus takes on the same form as the Patronus of his father, James Potter. Just like Minerva McGonagall, James Potter's Patronus matches his Animagus form. Similar to his father, Harry is a proud and strong and leader. Stags are thought to be kings of the forest and symbolize some of Harry's most defining traits.
When Harry first sees the stag Patronus in Harry Potter and the Prisoner of Azkaban, he thinks it's his father casting it, but it's actually Harry casting it when he time travels via Hermione's time-turner.