What is the name of the three headed dog in Harry Potter and the Sorcerer's Stone?

The three-headed dog in Harry Potter and the Sorcerer's Stone is named Fluffy. Fluffy, a massive and intimidating creature, guards the trapdoor leading to the Philosopher's Stone. Fluffy's name is derived from the fact that he has a very thick and shaggy fur. The name "Fluffy" contrasts with his ferocious appearance, adding a touch of humor to the character.