Mr. and Mrs. Dursley are a well-to-do and status-conscious couple living in provincial England. Their desire for middle-class normality is marred only by Mrs. Dursley's eccentric sister, Mrs. Potter, with whom she does not speak. One day, Mr. Dursley notices strange happenings on his way to work. That night, Albus Dumbledore, Professor McGonagall, and Hagrid assemble outside the Dursley home. Dumbledore tells McGonagall that someone named Voldemort--whom we later learn to be an evil wizard in pursuit of the Sorcerer's Stone--has killed the Potters, and tried unsuccessfully to kill their baby son Harry as well. After his failure Voldemort has fled. They leave Harry with an explanatory note in a basket in front of the Dursley home.
Ten years later, the Dursley household is dominated by the spoiled boy Dudley, who torments and bullies the young Harry. Dudley is loaded with presents while Harry is forced to sleep in a cupboard under the stairs. On Dudley's birthday, the Dursleys are forced to allow Harry to go along to the zoo. While Dudley is looking at a boa constrictor, the glass in front of it disappears, frightening everyone. Harry is punished for this at home.
As Harry prepares to go off to high school, mysterious letters begin coming to him at the Dursley house. Mr. Dursley is worried by the letters, and tries to keep them from Harry; he nails up the mail slot. But the letters keep arriving through every crack in the house. Finally, flees with his family to a secluded island house on a stormy night--the night of Harry's birthday. At midnight, they hear a large bang on the door and an oafish, blunt, but kindly giant named Hagrid enters. Hagrid hands Harry an admissions letter to the Hogwarts School of Witchcraft and Wizardry. Mr. Dursley protests, but is shut up by Hagrid. Harry learns that the Dursleys have tried to deny Harry's wizardry all these years. The next day, Hagrid takes Harry to London to shop for school supplies. First they go to the wizard bank, Gringotts, where Harry learns that his parents have left him a hefty supply of money. They shop on the wizards' commercial street known as Diagon Alley, where Harry is fitted for his school uniform, meeting an unpleasant fellow student who will later be identified as Draco Malfoy. Harry buys books, ingredients for potions, and finally, a magic wand. Harry's is the companion wand to the one belonging to the evil Voldemort.
Harry's last month with the Dursleys is uneventful. Finally Mr. Dursley takes Harry to London and drops him at the train station, where Harry catches his train to Hogwarts on track nine and three quarters. On the train, Harry befriends other first-year students like Ron and Hermione, a Muggle girl chosen to attend Hogwarts. When the train arrives at school, the first years are ushered by Professor McGonagall into a great hall, where they take turns putting on the "sorting hat" to find out in which residential house they will live. They glimpse the Hogwarts faculty, including Snape, professor of Potions, Quirrell, professor of Defense against the Dark Arts, and others. Presiding over the gathering is the magnificent figure of Dumbledore, renowned wizard and head of Hogwarts. Harry dreads being assigned to the sinister Slytherin house, but he and Ron are both placed in a house called Gryffindor.
As the school year gets underway, Harry discovers that his Potions professor, Snape, does not like him. Harry discusses this with Hagrid over tea, but Hagrid reassures him that Snape has no reason to dislike Harry. During the first flying lesson, the students are told to stay grounded while the teacher takes a student to the hospital. Disobediently, Draco Malfoy snatches a student's prized toy and flies off with it to the top of a tree.
Harry flies after him. Malfoy throws the ball in the air, and Harry speeds downward, making a spectacular catch. Professor McGonagall happens to witness this. Instead of punishing Harry, she recommends that he play Quidditch, a much-loved game like basketball played on broomsticks, for Gryffindor. Later that day, Malfoy challenges Harry to a wizard's duel at midnight. Malfoy doesn't show up at the appointed place, and Harry almost gets in trouble; trying to hide, he accidentally discovers a fierce three headed dog guarding a trapdoor in the forbidden third floor corridor. Harry and Ron discuss what might he guarded.
As the entire school is sitting down to Halloween dinner, a troll is found in the building. The students are all escorted back to their dormitories, but Harry and Ron sneak off to find Hermione, who is alone and unaware of the troll. Unwittingly they lock the troll in the girls' bathroom along with Hermione. Together, they defeat the troll. Hermione tells a lie to protect Harry and Ron from being punished, and from that moment on they are all friends. During Harry's first Quidditch match, his broom jerks out of control. Hermione notices Snape staring at Harry and muttering a curse. She concludes that he is jinxing Harry's broom, and sets his clothes on fire. Harry regains control of the broom and makes a spectacular play to win the Quidditch match.
For Christmas, Harry receives an invisibility cloak that used to belong to his father. He uses this to explore the school, unseen, late at night. He discovers the Mirror of Erised, a mirror that displays one's deepest desire to whoever looks in it. In it, Harry sees his parents alive. After Christmas, Harry, Ron and Hermione begin to unravel the mysterious connection between the Gringotts break-in and the three-headed guard dog. They learn that the dog is guarding the only known Sorcerer's Stone, belonging to Nicholas Flamel, Albus Dumbledore's old partner. Someone has been trying to steal the Sorcerer's Stone, capable of providing eternal life and unlimited wealth to its owner.
A few weeks later, Hagrid wins a dragon egg in a poker game. Since it is illegal to own dragons, Harry, Ron and Hermione contact Ron's older brother, who studies Dragons, and arrange to get rid of the dragon. In the process, they get caught out of bed late at night. Harry, Ron, and Hermione are severely punished: Gryffindor is docked 150 points. Furthermore, part of their punishment is to go into the enchanted forest with Hagrid to find out who has been killing unicorns recently. In the forest, Harry comes upon a hooded man drinking unicorn blood. The man tries to attack Harry, but Harry is rescued by a friendly centaur who tells him that his assailant was Voldemort. Harry also learns that it is Voldemort who has been trying to steal the Stone.
Harry has a hard time concentrating on his exam preparation, fearing that Voldemort will steal the Stone and kill him. He makes it through his exams anyway. Harry learns that Hagrid had accidentally let Voldemort know the secret of how to get past the guard dog. Harry suspects that Voldemort now knows how to get the Stone, and decides that he must find the Stone before Voldemort can get to it. He, Ron, and Hermione sneak off that night to the forbidden third floor corridor. They get past the guard dog, and perform many impressive feats as they get closer and closer to the Stone. In the end, Harry finds himself face to face with Quirrell. Harry is surprised it is Quirrell rather than Snape who has been orchestrating the theft; Quirrell explains that his shyness was only an act. Quirrell announces that Harry must die. Knowing that Harry desires to find the Stone, Quirrell first puts Harry in front of the Mirror of Erised, and makes him state what he sees. Harry sees himself with the Stone in his pocket, and at that same moment actually feels the Stone in his pocket. But he lies and tells Quirrell that he sees something else. A voice tells Quirrell that the boy is lying, and requests to speak to Harry face to face. Quirrell removes his turban and reveals Voldemort's face on the back of his head; Voldemort inhabits Quirrell's body. Voldemort tells Quirrell to kill Harry, but Quirrell is burned by contact with the boy. A struggle ensues and Harry passes out.
When Harry regains consciousness, he is in the hospital with Dumbledore. Dumbledore explains that he saved Harry from Quirrell just in time. He and Flamel have decided to destroy the Stone. Harry heads down to the end-of-year banquet, where Slytherin House is celebrating its seventh consecutive win of the house championship cup. Dumbledore gets up and awards many last-minute points to Gryffindor House for the feats of Harry and his friends, winning the house cup for Gryffindor. Harry returns to London and is met by his uncle, to spend the summer with the Dursleys.