The novel opens with a description of the Dursley family, a middle-class family that lives in Little Whinging, Surrey. Vernon and Petunia Dursley are constantly worried that someone will find out about Petunia’s decidedly “unDursleyish” witch sister, Lily, and their worries are justified when Lily’s infant son, Harry, is left on their doorstep. Lily and her husband, James Potter, had been murdered by the dark wizard, Voldemort, but when Voldemort attempted to kill Harry, his power somehow broke. Harry becomes the only living person ever to survive the killing curse, and the only sign of his encounter with Voldemort is a unique lightning bolt-shaped scar on his forehead. Because Harry does not have any other living relatives, Albus Dumbledore, the headmaster of Hogwarts School of Witchcraft and Wizardry, decides to leave him with the Dursleys until he is old enough to attend Hogwarts.
After ten years, Harry has grown to become a pale, skinny boy with black hair that sticks up all over the place and bright green eyes. From a young age, Harry is told that his parents were killed in a car crash but has no other information about them, not even a photograph. Harry’s cousin Dudley dominates the household, bullying Harry with his gang of friends and being spoiled rotten by Uncle Vernon and Aunt Petunia. While Dudley has two bedrooms– one for his bed and one for all of his broken toys – Harry is relegated to the small cupboard under the stairs. Although he strives to avoid attracting attention, Harry cannot deny that strange things often happen around him. Once Aunt Petunia cut off all of his hair in a fit of frustration, and it grew back to its original length in time for school the next day. Another time, Harry was being chased by Dudley’s gang and suddenly found himself on the kitchen roof.
On Dudley’s eleventh birthday, Harry accompanies the family and Dudley’s best friend, Piers Polkiss, to the zoo. While Harry is in the reptile house, the glass front of the boa constrictor cage suddenly vanishes. Harry is unable to explain the incident, but Uncle Vernon blames him anyway and restricts him to the cupboard under the stairs until the summer holidays. One day, mysterious letters begin to arrive for Harry. Uncle Vernon refuses to let Harry read the letter but tells him that it was addressed to him by mistake. Over the next few days, more and more of the letters arrive in the house, but Uncle Vernon keeps Harry from intercepting any of them. In an extreme effort to escape from the letters, Uncle Vernon takes the family to a desolate shack on an island on the night before Harry’s eleventh birthday.
As the clock strikes midnight and Harry wishes himself a silent “Harry Birthday,” there is a loud bang on the door and Hagrid enters. Hagrid introduces himself as the Keeper of the Keys at Hogwarts and then explains that Harry is a wizard who has been admitted to Hogwarts in order to study magic. Harry discovers that the Dursleys have always been aware of his magical abilities but have attempted to stifle them and make him “normal.” Moreover, Harry learns the truth about his parents’ murder by Voldemort.
The following day, Hagrid takes Harry to Diagon Alley in London to shop for school supplies. Their first stop is the wizarding bank, Gringotts, where Harry is shown to his family vault and realizes that his parents have left him with a comfortable fortune of wizarding gold. During their trip to the bank, Hagrid makes a stop at Vault 713 and removes a mysterious package: Hogwarts business for Dumbledore, he explains. After the bank, Harry visits Madam Malkin’s Robes for All Occasions for his plain black school robes and Flourish and Blotts for his magical school textbooks, as well as other shops for parchment and potion ingredients. Hagrid buys Harry a snowy owl as a birthday present, and Harry decides to name her Hedwig. Their last stop in Diagon Alley is Ollivander’s, where Harry purchases a magic wand that contains a matching core to the evil Voldemort’s wand.
A month later, Harry leaves Little Whinging to catch the Hogwarts Express, which leaves King’s Cross Station from Platform Nine and Three-quarters. At first, he is uncertain how to access the wizard platform, but he receives help from Molly Weasley, who shows him how to reach the train. While on the train, Harry befriends Ron Weasley and Hermione Granger, two first-year students with their own insecurities about entering Hogwarts: as the youngest of five brothers who have achieved success at Hogwarts, Ron worries about distinguishing himself, while Hermione is anxious about her background as a Muggle-born. Harry also meets Neville Longbottom, a slightly dopey first-year with a pet toad named Trevor, and Draco Malfoy, an unpleasant student who arrogantly offers to advise Harry on who to be friends with.
When the train arrives at Hogwarts, the students immediately file into the dining hall to be “sorted,” or assigned to one of the four houses of Hogwarts: Gryffindor, Slytherin, Hufflepuff, and Ravenclaw. Harry worries that he will be sorted into Voldemort’s old house, Slytherin, and he makes a special request to the Sorting Hat to be assigned to any other house. The Sorting Hat considers carefully but ultimately places Harry (as well as Ron and Hermione) in Gryffindor House.
As the school year begins, Harry receives more attention than he ever has before, especially when the other students catch sight of his lightning bolt-shaped scar. Although most of his classes are enjoyable, Professor Snape, the potions instructor, seems determined to dislike Harry, and Harry notices that his scar seems to prickle whenever Snape glares at him. After their first potions lesson, Harry and Ron decide to visit Hagrid at his cottage near the Forbidden Forest. Hagrid inadvertently reveals that Vault 713, the Gringotts vault containing the mysterious package, was broken into shortly after Harry and Hagrid’s visit to Diagon Alley.
During their first flying lesson, Neville breaks his wrist and must be taken to the hospital wing by the instructor. Malfoy grabs Neville’s Remembrall—forgotten after his injury—and flies into the air with it. Harry flies after Malfoy to retrieve Neville’s toy and, when Malfoy throws the Remembrall to the ground, makes a spectacular dive to catch the Remembrall mere inches from the ground. Professor McGonagall observes Harry’s skilled flying and, instead of punishing him for breaking the rules, sets him up to play Seeker on the Gryffindor Quidditch team.
Malfoy arranges a midnight duel with Harry to settle the score, and Ron, Hermione, and Neville accompany him to make sure that he stays out of trouble. The four accidentally enter a forbidden corridor and come across a three-legged dog standing guard over a trapdoor. They leave the corridor quickly, but not before Harry has concluded that the dog is guarding the mysterious package from Vault 713.
On Halloween, the faculty is alerted of a wayward troll in the school and escort the students back to their houses. Harry and Ron sneak away to find Hermione, who is in the girl’s bathroom and missed the warning. After inadvertently locking the troll in the girl’s bathroom with Hermione, Ron and Harry knock the troll unconscious. Hermione takes the blame for the battle, and the three become fast friends. During Harry’s first Quidditch match, his broom is jinxed by a mysterious source. Hermione and Ron assume that Snape is jinxing Harry after Hermione sees Snape muttering to himself. She sets Snape’s robes on fire in time for Harry to regain control of his broom and win the game with a spectacular catch.
Harry stays at Hogwarts with Ron over the Christmas holidays and spends time playing wizard’s chess and researching Nicolas Flamel, who Hagrid accidentally mentioned in connection with the package from Vault 713. On Christmas morning, Harry is surprised to receive numerous presents, including a rare invisibility cloak. The note accompanying the cloak says that it belonged to Harry’s father. That night, Harry decides to try out his invisibility cloak and comes across a large mirror in the middle of a room. When he looks in the mirror, he sees his dead parents and other unknown relatives staring back at him. The next night, Harry rushes back to the room to see his family in the mirror and is surprised by Professor Dumbledore, who has been waiting for him. Dumbledore explains that the Mirror of Erised reveals the deepest desires of a person’s heart but cannot give truth or knowledge. Dumbledore also tells Harry that the mirror will be moved to a new location the following day, and Harry should not try to find it again.
After the holidays end, Harry, Ron, and Hermione finally discover the identity of Nicolas Flamel: he is the only known maker of the Sorcerer’s Stone, which produces the elixir of life. They realize that the three-headed dog is guarding the Sorcerer’s Stone, and Harry begins to suspect that Snape is planning to steal it. Harry, Ron, and Hermione also discover that Hagrid is raising an illegal dragon that was given to him by a mysterious stranger in a bar in exchange for information about the three-headed dog. Harry and Hermione decide to smuggle the dragon to Ron’s brother, Charlie, who works with dragons in Romania, but are caught just after handing off the dragon to one of Charlie’s friends.
As punishment for disobeying school curfew, Harry and Hermione (as well as Malfoy and Neville, who were also out of bed at the time) are sent into the Forbidden Forest with Hagrid to locate a wounded unicorn. When the group splits into two, Harry and Malfoy come across the body of the unicorn just as a hooded figure crawls toward it and starts to drink its blood. Malfoy screams and runs away, but Harry is frozen in place by an agonizing pain that is suddenly spreading from his scar. As the hooded figure moves toward him, a centaur gallops in front of Harry protectively and the figure disappears. The centaur suggests that the hooded figure was Voldemort and that he drank the unicorn’s blood in order to stay alive until he can steal the Sorcerer’s Stone.
Harry decides to steal the Sorcerer’s Stone before Voldemort can. Harry, Ron, and Hermione sneak off to the forbidden corridor and get past the three-headed dog by lulling it to sleep with music. Once through the trap door, they land on Devil’s Snare, the first of several challenges put in place by the Hogwart’s teachers. As the plant’s snake-like tendrils threatened to strangle Ron and Harry, Hermione uses magical fire to repel the plant and break them free. The next challenge is to pass through a room filled with hundreds of small flying keys. Harry flies on a broomstick to find the silver key that matches the lock on the door and finally snatches it out of the swarm. The door opens to reveal a giant wizard’s chessboard. An expert chess player, Ron takes the lead in this challenge and ultimately sacrifices himself in order to allow Harry and Hermione to reach the next challenge. When Harry and Hermione step into the next room, they are instantly surrounded by flames and faced with a complex riddle of poisonous potions. Hermione rationally solves the riddle and gives Harry the potion needed to travel to the next room and the final challenge while she returns to help Ron.
In the final chamber, Harry is surprised to find neither Snape nor Voldemort, but Professor Quirrell, the meek-tempered teacher of Defense against the Dark Arts, and the Mirror of Erised. Quirrell reveals that he, not Snape, has been Voldemort’s servant all along: Quirrell jinxed Harry’s broom during the Quidditch match and drank the unicorn’s blood in the Forbidden Forest. Now, in the final challenge, Quirrell needs only to retrieve the Sorcerer’s Stone from within the Mirror of Erised. He asks his master for help, and Harry hears a disembodied voice speak from within Quirrell, telling him to use Harry to get to it. Quirrell stands Harry in front of the mirror and orders him to tell him what he sees. Determined to keep the Stone from falling into Voldemort’s hands, Harry lies and tells Quirrell that he sees himself winning the Quidditch Cup for Gryffindor. He then actually sees himself holding the Sorcerer’s Stone and putting it in his pocket. Realizing that the Stone is now in his pocket, Harry tries to stall for time until he can escape. Quirrell removes his turban and reveals Voldemort’s face emerging from the back of his head. Voldemort speaks directly to Harry, taunting him about the death of his parents, and then orders Quirrell to kill him. When Quirrell tries to touch Harry, his skin blisters and, though Harry is in excruciating pain from his scar, he forces the contact with Quirrell. With Voldemort’s screams of anger echoing in his head, Harry finally passes out.
When Harry wakes up, he finds himself in the hospital wing with Dumbledore. Dumbledore found Harry just in time to keep Quirrell from killing him, though Voldemort escaped once again. Dumbledore explains that Quirrell was unable to touch Harry’s skin because of his mother’s love: when Lily Potter sacrificed herself for him, she left Harry with an ancient magical protection. He knew that only Harry would be able to retrieve the Stone from the Mirror of Erised because, unlike Quirrell and Voldemort, Harry wanted to find the Stone but did not want to use it. Although Voldemort was not destroyed, Harry’s actions have kept him from regaining power for now.
At the end of the year banquet, the members of Slytherin House are celebrating their victory of the House Cup for the seventh straight year. Unexpectedly, Dumbledore awards last-minute points to Harry, Ron, Hermione, and Neville, which gives Gryffindor the edge over Slytherin. Harry considers it to be the best night of his life and returns to spend the summer with the Dursleys content in the friendships that he has made at Hogwarts.