Voldemort makes his first Horcrux out of his boyhood diary when he murders a girl named Myrtle, who becomes the ghostly Moaning Myrtle. Tom Riddle is Voldemort's original name, and a fragment of young Tom Riddle lives on in the Horcrux, exchanging messages with those who write in the diary and bewitching them to do his evil bidding. Harry destroys this Horcrux by stabbing it with a basilisk fang in "Harry Potter and the Chamber of Secrets."
The second Horcrux is Marvolo Gaunt's ring, an heirloom of the pure-blooded Peverell wizarding family. Voldemort hides the ring in the dilapidated Gaunt house, where Tom Riddle's mother had lived. Professor Dumbledore kills this Horcrux by striking it with the sword of Gryffindor, but not before first trying on the ring, which releases a deadly curse upon him and withers his hand.
Harry and his friends find the third Horcrux, a gold cup once belonging to Helga Hufflepuff, in the Lestrange vault at Gringotts bank. Hermione Granger destroys the Horcrux by stabbing it with a basilisk fang.
The fourth Horcrux, Salazar Slytherin's locket, travels far and wide. Regulus Black and his house-elf Kreacher steal the locket from Voldemort's hiding spot in an oceanside cave. Mundungus Fletcher then sneaks the locket out of the Black home, and Harry, Ron and Hermione eventually recover it from Dolores Umbridge. Ron smashes the locket with Godric Gryffindor's sword and kills the piece of soul residing within.
Harry and his friends find Rowena Ravenclaw's diadem, the fifth Horcrux, at Hogwarts Castle in the Room of Requirement. Pursued by Crabbe, Goyle and Draco Malfoy, Harry barely escapes before Crabbe's Fiendfyre curse consumes the room and everything in it. He grabs the burning diadem as he flees. Because Fiendfyre, or cursed fire, is one of the few means of destroying Horcruxes, Crabbe unknowingly finishes off this bit of Voldemort's soul.
Dumbledore long suspects that Voldemort's pet snake, Nagini, is the sixth Horcrux. He is proven right in "Harry Potter and the Deathly Hallows" when Neville Longbottom slays Nagini with the sword of Gryffindor, thereby removing the last Horcrux standing between Voldemort and death.
"You were the seventh Horcrux, Harry, the Horcrux he never meant to make," Dumbledore explains at the end of "Deathly Hallows." In the course of murdering Harry's parents and attempting to kill Harry, Voldemort unintentionally makes a Horcrux out of Harry, one that operates under different rules. Harry and Voldemort are tied together, sometimes accessing each other's thoughts, and unable to kill each other for most of the saga. When Harry sacrifices himself, Voldemort's Killing Curse destroys the Horcrux within Harry while leaving Harry's body unharmed.