Daniel Radcliffe as Harry Potter: A seemingly normal child with a lightning shaped scar on his forehead and an ability to make strange things happen. He was raised by his aunt and uncle from the age of one year, following the death of his parents, about whom he knows very little. On his eleventh birthday Harry discovers that he is a wizard. Harry then attends Hogwarts School of Witchcraft and Wizardry, where he is sorted into Gryffindor House.
Emma Watson as Hermione Granger: An extremely intelligent witch who was "Muggle-born". Despite initially irritating them, she becomes friends with Harry and Ron after the pair save her from a cave troll. She is sorted into Gryffindor.
Rupert Grint as Ron Weasley: A red haired wizarding boy, one of seven children of a disadvantaged family. Ron meets Harry on the Hogwarts Express and develops a long standing friendship with him. He is sorted into Gryffindor with Harry.
Bonnie Wright as Ginny Weasley: Ron's sister who accompanies Harry to the Department of Mysteries.
Tom Felton as Draco Malfoy: A wizard from a rich background. After Harry rejects his initial offer of "friendship", Draco develops an ever lasting hatred of Harry and his friends. He is sorted into Slytherin.
Matthew Lewis as Neville Longbottom: A timid student who is a friend of Harry, Ron and Hermione. He is the frequent target of Malfoy and his gang.
Chris Rankin as Percy Weasley: Ron's pompous older brother and the Hogwarts Head Boy.
Katie Leung as Cho Chang: Harry's love interest.
Evanna Lynch as Luna Lovegood: a classmate of Harry's who explains the Thestrals to him and accompanies him to the Department of Mysteries.
Harry Melling as Dudley Dursley: Harry's over-weight and spoilt cousin.
Richard Harris as Albus Dumbledore: The Headmaster of Hogwarts. He is one of the most famous and powerful wizards of all time, having in the past defeated the dark wizard Grindelwald. He took Harry to his aunt and uncle following the death of Lily and James Potter at the hands of Lord Voldemort.
Robbie Coltrane as Rubeus Hagrid: A half-giant and the Groundskeeper at Hogwarts. He takes Harry to Privet Drive on a flying motorcycle, then takes him from his aunt and uncle on his eleventh birthday, after which the two develop a strong bond. He has a fondness for magical creatures, in particular dragons.
Alan Rickman as Severus Snape: The Potions Master and head of Slytherin House at Hogwarts. He dislikes Harry due to a grudge against Harry's father. He is a former Death Eater but is trusted by Dumbledore.
Maggie Smith as Minerva McGonagall: The Deputy Headmistress, head of Gryffindor and Transfiguration teacher at Hogwarts. She accompanies Dumbledore to Number 4 Privet Drive when Harry is taken to his aunt and uncle. She has the ability to transform into a tabby cat.
Ian Hart as Professor Quirrell: The slightly nervous Defence-Against the Dark Arts Teacher at Hogwarts. He sports a purple turban, which harbours the near dead form of Lord Voldemort underneath.
Gary Oldman as Sirius Black: An escapee from the wizarding prison Azkaban and Harry's godfather. Despite what the wizarding world believes, he is actually completely innocent.
Imelda Staunton as Dolores Umbridge: the new Defence Against the Dark Arts teacher, a plant from the Ministry of Magic who prevents Harry and his friends from learning practical magic, and refuses to allow Harry to claim that Lord Voldemort has returned.
Ralph Fiennes as Lord Voldemort: the antagonist, who lures Harry to the Ministry of Magic and nearly kills him.
David Thewlis as Remus Lupin: The new Defence Against the Dark Arts teacher at Hogwarts, who is actually a werewolf. He was friends with Harry's parents when they were at school, and teaches Harry to conjure a Patronus Charm to fight the dementors.
Emma Thompson as Sybill Trelawney: The inept Hogwarts Divination teacher, who unknowingly predicts the return of Lord Voldemort.
Warwick Davis as Filius Flitwick: A small wizard, he is the Charms teacher and head of Ravenclaw at Hogwarts.