Harry Potter is a seemingly ordinary boy, living with his negligent relatives, the Dursleys. On his eleventh birthday, Harry learns from a mysterious stranger, Rubeus Hagrid, that he is actually a wizard, famous in the Wizarding World for surviving an attack by the evil Lord Voldemort when Harry was only a year old. Voldemort killed Harry's parents, but his attack on Harry rebounded, leaving only a lightning-bolt scar on Harry's forehead and rendering Voldemort powerless. Hagrid reveals to Harry that he has been invited to begin attending Hogwarts School of Witchcraft and Wizardry. After buying his school supplies from the hidden wizarding street Diagon Alley, Harry boards the train to Hogwarts via the concealed platform 9¾.
On the train leading to Hogwarts, Harry meets Ron Weasley, a boy from a large wizarding family, and Hermione Granger, a witch born to non-magical parents. Once they arrive at the school, Harry and all of the other first-year students are sorted into four different houses: Gryffindor, Hufflepuff, Ravenclaw, and Slytherin. As Slytherin is noted for being the house of darker wizards and witches, Harry successfully begs the magical Sorting Hat not to put him in Slytherin. He winds up in Gryffindor, along with Ron and Hermione.
At Hogwarts, Harry begins learning wizardry and also discovers more about his past and his parents. Harry inadvertently makes Gryffindor's Quidditch team as a Seeker, learning that his father was also a member of the team. One night, he, Ron, and Hermione find a giant three-headed dog on a restricted floor at the school. The dog is guarding the Philosopher's Stone, an item that can be used to grant its owner immortality. Harry concludes that his potions teacher, Severus Snape, is trying to obtain the stone in order return Voldemort to a human form.
After hearing from Hagrid that the dog will fall asleep if played music, Harry, Ron, and Hermione decide to get to it and find the stone before Snape does. They face a series of tasks, which include surviving a deadly plant, flying past hundreds of flying keys trying to find one to unlock a door, and winning a violent, life-sized chess match. After getting past the tasks, Harry finds out that it was not Snape who wanted the stone, but Defence Against the Dark Arts teacher Professor Quirrell. Quirrell removes his turban and reveals Voldemort to be living on the back of his head. Voldemort tries to convince Harry to give him the stone (which Harry suddenly finds in his pocket as the result of an enchantment by the headmaster, Albus Dumbledore), by promising to bring his parents back from the dead, but Harry refuses. Quirrell tries to kill him but Harry's touch burns him to death. When Harry gets up, Voldemort's spirit forms and passes through Harry, knocking him unconscious, before fleeing.
Harry wakes up in the school's hospital wing, with Professor Dumbledore at his side. Dumbledore explains that the stone has been destroyed, and that, despite Ron's nearly being killed in the chess match, both Hermione and Ron are fine. The reason Quirrell burned at Harry's touch was because when Harry's mother died to save him, her death gave Harry a magical, love-based protection against Voldemort. Before Harry and the rest of the students leave for the summer, Harry realizes that while every other student is going home, Hogwarts is truly his home.
