Before the start of the novel, Voldemort, considered the most evil and powerful dark wizard in history, kills Harry's parents but mysteriously vanishes after trying to kill the infant Harry. While the wizarding world celebrates Voldemort's downfall, Professor Dumbledore, Professor McGonagall and Rubeus Hagrid place the one year-old orphan in the care of his neglectful and abusive Muggle (non-wizard) uncle and aunt: Vernon and Petunia Dursley, who have a son, Dudley, a spoiled and selfish boy.
For ten years, Harry is tormented by the Dursleys. Shortly before his eleventh birthday, a series of letters addressed to Harry arrive, but Vernon destroys them before Harry can read them, leading only to an influx of more letters. To get away from the letters, Vernon takes the family to a small island. As they are settling in, Hagrid bursts through the door to tell Harry what the Dursleys have kept from him: Harry is a wizard and has been accepted at Hogwarts.
Hagrid takes Harry to Diagon Alley, a magically concealed shopping precinct in London, where Harry is bewildered to discover how famous he is among wizards as "the boy who lived." He also finds that he is quite wealthy, since a bequest from his parents has remained on deposit at Gringotts Wizarding Bank. Guided by Hagrid, he buys the equipment he needs for Hogwarts. At the wand shop, he finds that the wand that suits him best is the twin of Voldemort's; both wands contain feathers from the same phoenix.
A month later, Harry leaves the Dursleys' home to catch the Hogwarts Express from King's Cross railway station. There he meets the Weasley family, who show him how to pass through the magical wall to Platform 9¾, where the train is waiting. While on the train, Harry makes friends with Ron Weasley, who tells him that someone tried to rob a vault at Gringotts. During the ride, they meet Hermione Granger. Another new pupil, Draco Malfoy, accompanied by his sidekicks Vincent Crabbe and Gregory Goyle, offers to advise Harry, but Harry dislikes Draco's arrogance and prejudice.
Before the term's first dinner in the school's Great Hall, the new pupils are allocated to houses by the Sorting Hat. Before it is Harry's turn, he catches Professor Snape's eye and feels a pain in the scar Voldemort left on his forehead. While Harry is being sorted, the Hat wonders whether he should be in Slytherin, but when Harry objects, the Hat sends him to Gryffindor.
After a terrible first Potions lesson with Snape, Harry and Ron visit Hagrid, who lives in a cabin on the edge of the Forbidden Forest. There they learn that the attempted robbery at Gringotts happened the day Harry withdrew money. Harry remembers that Hagrid had removed a small package from the vault that had been broken into.
During the new pupils' first broom-flying lesson, Neville Longbottom breaks his wrist, and Draco takes advantage to throw the forgetful Neville's fragile Remembrall high in the air. Harry gives chase on his broomstick, catching the Remembrall inches from the ground. Professor McGonagall dashes out and appoints him as the new Seeker for the Gryffindor Quidditch team.
When Draco tricks Ron and Harry, who are accompanied by Neville and Hermione Granger, into a midnight excursion, they accidentally enter a forbidden corridor and find a huge three-headed dog. The group hastily retreats, and Hermione notices that the dog is standing over a trap-door. Harry concludes that the monster is guarding the package Hagrid retrieved from Gringotts.
After Ron criticises Hermione's ostentatious proficiency in Charms, she hides in the girls' toilet, crying. At the Halloween Night dinner, Professor Quirrell reports that a troll has entered the dungeons. While everyone returns to their dormitories, Harry and Ron rush to warn Hermione. The troll corners Hermione in the toilet but Harry and Rone clumsily save her. Afterwards, Hermione takes the blame for the battle and becomes a firm friend of the two boys.
The evening before Harry's first Quidditch match, he sees Snape receiving medical attention from Filch for a bite on his leg caused by the three-headed dog. During the game, Harry's broomstick goes out of control, endangering his life, and Hermione notices that Snape is staring at Harry and muttering. She dashes over to the Professors' stand, knocking over Professor Quirrell in her haste, and sets fire to Snape's robe. Harry regains control of his broomstick and catches the Golden Snitch, winning the game for Gryffindor. Hagrid refuses to believe that Snape was responsible for Harry's danger, but lets slip that he bought the three-headed dog and that the monster is guarding a secret that belongs to Professor Dumbledore and someone called Nicolas Flamel.
Harry and the Weasleys stay at Hogwarts for Christmas, and one of Harry's presents, from an anonymous donor, is an Invisibility Cloak owned by his father. Harry uses the Cloak to search the library's Restricted Section for information about the mysterious