Final book

In Harry Potter and the Deathly Hallows, Harry, Ron, and Hermione leave Hogwarts to complete Dumbledore's task: to search for and destroy Voldemort's remaining four Horcruxes, then find and kill the Dark Lord. The three pit themselves against Voldemort's newly formed totalitarian police state, an action that tests Harry's courage and moral character. Voldemort's seizure of the Ministry of Magic leads to discriminatory and genocidal policies against Muggle-borns, fuelled by propaganda and fear. According to J. K. Rowling, telling scenes are when Harry uses Cruciatus Curse and Imperius Curse, unforgivable curses for torture and mind-control, on Voldemort's servants, and also when he casts Sectumsempra on Draco Malfoy during the bathroom fight in the sixth book. Each time shows a "flawed and mortal" side to Harry. However, she explains, "He is also in an extreme situation and attempting to defend somebody very good against a violent and murderous opponent.

Harry experiences occasional disturbing visions of Draco being forced to perform the Death Eaters' bidding and feels "...sickened...by the use to which Draco was now being put by Voldemort," again showing his compassion for an enemy.

Each Horcrux Harry must defeat cannot be destroyed easily. They must be destroyed with basilisk venom, Godric Gryffindor's sword, or some other destructive substance. In Book Two, Harry destroys the first horcrux, Tom Riddle's diary, with a basilisk fang, and in Book Six Dumbledore destroys the ring with Gryffindor's sword. Ron destroys Slytherin's locket with the sword, Hermione destroys Hufflepuff's cup with a basilisk fang, and Crabbe destroys Ravenclaw's diadem with Fiendfyre (cursed flame). Neville kills the snake Nagini with the sword, and Voldemort destroys the final accidental Horcrux: a fragment of soul embedded in Harry's scar.

Harry comes to recognise that his own single-mindedness makes him predictable to his enemies and often clouds his perceptions. When Voldemort kills Snape later in the story, Harry realises that Snape was not the traitorous murderer he believed him to be, but a tragic antihero who was loyal to Dumbledore. In Chapter 33 ('The Prince's Tale') Snape's memories reveal that he loved Harry's mother Lily, but their friendship ended over his association with future Death Eaters and his "blood purity" beliefs. When Voldemort murdered the Potters, a grieving Snape vowed to protect Lily's child, although he loathed young Harry for being James Potter's son. The memories also reveal that Snape did not murder Dumbledore, but carried out Dumbledore's prearranged plan. Dumbledore, dying from a slow-spreading curse, wanted to protect Snape's position within the Death Eaters and to spare Draco from completing Voldemort's task of murdering him.

To defeat Harry, Voldemort steals the most powerful wand ever created, the Elder Wand, from Dumbledore's tomb and twice casts the Killing Curse on Harry with it. The first attempt merely stuns Harry into a deathlike state; the murder attempt fails because Voldemort used Harry's blood in his resurrection during book four. The protection that his mother gave Harry with her sacrifice tethers Harry to life, as long as his blood and her sacrifice run in the veins of Voldemort. In the chapter "King's Cross," Dumbledore's spirit talks to Harry whilst in this deathlike state. Dumbledore informs Harry that when Voldemort disembodied himself during his failed attempt to kill Harry as a baby, Harry became an unintentional Horcrux; Harry could not kill Voldemort while the Dark Lord's soul shard remained within Harry's body. The piece of Voldemort's soul within Harry was destroyed through Voldemort's first killing curse with the Elder Wand because Harry willingly faced death.

In the book's climax, Voldemort's second Killing Curse hurled at Harry also fails and rebounds upon Voldemort, finally killing him. The spell fails because Harry, not Voldemort, had become the Elder Wand's true master and the wand could not harm its own master. Harry has each of the Hallows (the Invisibility Cloak, the Resurrection Stone, and the Elder Wand) at some point in the story but never unites them. However, J. K. Rowling said the difference between Harry and Voldemort is that Harry willingly accepts mortality, making him stronger than his nemesis. "The real master of Death accepts that he must die, and that there are much worse things in the world of the living." At the very end, Harry decides to leave the Elder Wand in Dumbledore's tomb and the Resurrection Stone hidden in the forest, but he keeps the Invisibility Cloak because it had belonged to his father.

Epilogue

In the epilogue of Deathly Hallows, which is set 19 years after Voldemort's death, Harry and Ginny are a couple and have three children: James Sirius Potter, who has already been at Hogwarts for at least one year, Albus Severus Potter, who is starting his first year there, and Lily Luna Potter, who is two years away from her first year at the school.

According to Rowling, after Voldemort's defeat, Harry joins the "reshuffled" Auror Department under Kingsley Shacklebolt's mentoring, and ends up eventually rising to become Head of said department in 2007. Rowling said that his old rival Draco has a grudging gratitude towards Harry for saving his life in the final battle, but the two are not friends. During the events of Harry Potter and the Cursed Child, however, Harry and Draco become friends after they join forces to save their respective sons.