Albus Percival Wulfric Brian Dumbledore is a renowned headmaster of Hogwarts School of Witchcraft and Wizardry, founder of the Order of the Phoenix and is regarded as one of the greatest wizards in history. He is a staunch supporter of Muggle rights and is highly opposed to the Dark Arts. Indeed, he is known by many as the only one Lord Voldemort is truly afraid of. Dumbledore is known for withholding many details from those he is involved with, but usually knows what he's doing, often playing a proverbial long game, his brilliant mind working overtime. He also possesses a very kind and trusting nature, allowing the expelled Hagrid to stay at Hogwarts as gamekeeper following his expulsion, and taking special precautions so the werewolf Remus Lupin can attend school.
Dumbledore hails from Mould-on-the-Wold, the oldest of his siblings, Aberforth and Ariana. Following Percival's imprisonment for attacking the three Muggle boys who attacked Ariana, Kendra Dumbledore moves the family to Godric's Hollow, a noted village where magical people and Muggles live in harmony. When Albus arrives at Hogwarts, with the instruction to hide his sister's condition, he quickly becomes one of the most popular and brilliant young wizards in Hogwarts' history and is soon in correspondence with the most notable magical names of the day, including Nicholas Flamel, creator of the Philosopher's Stone, and Bathilda Bagshot, the famed magical historian. Upon his graduation from Hogwarts, he intends to take a traditional world tour, but his plans are cut short by the death of Kendra, leaving Albus the head of the house. He is introduced by Bathilda to Gellert Grindelwald, an equally brilliant young wizard who has recently been expelled from Durmstrang and who Albus harbours romantic feelings for. The boys begin making plans for a wizarding new world order, which they would accomplish by obtaining the Deathly Hallows. The plan is all for the greater good, but it falls apart when Aberforth confronted them for neglecting Ariana and is cursed by Grindelwald. A duel erupts between all three, and Ariana is killed in the struggle.
Albus returns to Hogwarts where he becomes the Professor of Transfiguration. He is also offered the position of Minister for Magic several times, but declines, knowing that he can not be trusted with such a level of power. He later visits a London orphanage in search of a promising young wizard named Tom Riddle to offer him a place at Hogwarts. While at the time, Dumbledore is unaware than he has met who will become the most feared Dark Wizard in history, he does not trust Riddle, and keeps a close eye on him at Hogwarts. In 1945, Dumbledore re-encounters Grindelwald and engages him in a titanic duel, which Dumbledore eventually wins, taking the Elder Wand and imprisoning Grindelwald within Nurmengard, the prison his old friend had built to house his enemies. Following the retirement of Professor Dippet in 1956, Albus takes the position of Headmaster of Hogwarts and a short time later, he is approached by Tom Riddle, now fully immersed in his identity as Lord Voldemort and seeking to become Defence Against the Dark Arts teacher. Voldemort's doings have reached Dumbledore however, and he is refused the position: news which Voldemort does not take well. As Voldemort begins to slowly take over, Dumbledore heads up the resistance, and personally takes an interest in the safety of the Potters when it becomes clear that Voldemort intends to kill their infant son, Harry. Following the deaths of James and Lily however, Albus takes steps to ensure the safety of Harry, with assistance from Severus Snape who has defected from Voldemort after it became clear that Voldemort did not care about the safety of Lily, who Snape has always loved. This secret ensures that Severus is one of Dumbledore's most trusted allies, though it is never clear to his fellows or students as to why.
When the Philosopher's Stone is moved to Hogwarts, Dumbledore places the final level of protection upon it, using the Mirror of Erised as an obstacle and tool for obtaining the stone. The now 11 year old Harry is able to obtain and protect it from Quirinus Quirrell and Voldemort, though is saved at the last minute by Dumbledore, who Harry theorises wanted to give him a chance against Voldemort. A year later, Dumbledore is ordered to step aside by Lucius Malfoy, following a string of attacks on Muggle-borns from the Chamber of Secrets, though he later returns at the behest of the other governors, just as Harry has defeated the Basilisk within the Chamber, destroyed the diary containing a piece of Voldemort's soul and rescued Ginny Weasley, a pawn in the soul fragment's plan. Two years later, Voldemort returns to full strength at the end of the Triwizard Tournament, and Dumbledore, notified instantly by Harry, is able to recall the original Order of the Phoenix a mere hour after the Dark Lord's resurrection. Over the following year, Dumbledore resolutely avoids Harry, fearing the connection between him and Voldemort, while at the same time suffering relentless persecution at the hands of the Ministry and Daily Prophet who simply refuse to believe that Voldemort has returned. He is even replaced as Headmaster for a time, following his retreat from Ministry representatives, though the students, still loyal to him, resist the tyranny of Dolores Umbridge as much as possible. Dumbledore later arrives in the Ministry of Magic while Harry, a small group of DA members and the Order battle the Death Eaters over a prophecy record. When Voldemort himself arrives, Dumbledore takes on the Dark Lord single-handed, but is unable to defeat him as Voldemort retreats with Bellatrix Lestrange in tow.
Snape kills Dumbledore - Harry Potter and the Half-Blood Prince
A short time later, Dumbledore begins searching for information on how to help Harry ultimately destroy Voldemort, and begins researching the Horcruxes. He finds one, forgetting that the ring holding the Resurrection Stone has been turned into a container for Voldemort's soul, too excited at the prospect of owning another Deathly Hallow, and is immediately fatally cursed. He is able to return to Hogwarts and is saved by Snape, who is able to isolate the curse within one hand, but is unable to halt the spread of it forever. Dumbledore is also aware that Voldemort has made plans for his nemesis' execution at the hands of Draco Malfoy. Not wishing for a more or less innocent boy's soul to be damaged, Dumbledore instructs Snape to kill him when the time comes. With the best part of a year to live, Dumbledore sets about instructing Harry on Voldemort's past and the Horcruxes and allows the young wizard to accompany him in search of another one. They are able to break through the defences, not knowing that the real Horcrux was removed decades ago, though Dumbledore is severely weakened. Harry is able to return him to Hogsmeade and subsequently the school, where the dying Dumbledore encounters Malfoy and a small group of Death Eaters. When Snape arrives, he fulfils Dumbledore's request and casts the Killing Curse upon him, blasting him out of the Astronomy Tower, and retreats with the Death Eaters. Dumbledore's body is found at the foot of the tower, and an elaborate funeral is held for him a few days later, his body laid to rest in a magnificent white marble tomb in the grounds of Hogwarts.
Dumbledore effectively lives on in death however. His plans remain in motion, and a portrait of Dumbledore is quickly hung in the headmaster's office. In portrait form, Dumbledore regularly advises Snape on how he can surreptiously assist Harry and the Order in the battles against Voldemort and the trio's hunt for the remaining Horcruxes.