V is a mysterious anarchist vigilante and freedom fighter, easily recognizable by his Guy Fawkes mask and dark clothing.
V has a Military background in some form of Special Forces.
The background and identity of V is largely unknown. He was at one point an inmate at "Larkhill Resettlement Camp"—one of many concentration camps where political prisoners, homosexuals, Black people, Jews, Muslims, Indians, Pakistanis, and others deemed undesirable by the gov't are exterminated by Britain's new fascist regime. While there, he is part of a group of prisoners who are subjected to horrific medical experimentation, conducted by Dr. Delia Surridge, involving artificially-designed hormone injection. Lewis Prothero is the camp's commandant, and a paedophile vicar, Father Lilliman, is at the camp to lend "spiritual support". All prisoners so injected die slowly under gruesome circumstances, with the sole exception of "the man in room five" ("V" in Roman numerals). During that time, the man had some level of communication with Valerie Page, a former actress imprisoned for being a lesbian, kept in "room four", who wrote her autobiography on toilet paper and then pushed it through a hole in the wall.
Although there is nothing physically wrong with him, Surridge theorizes that his mind had been warped by the experimentation. Still, his actions seem to maintain a twisted logic. The experiments actually yield some beneficial results: he develops Olympic-level reflexes, increased strength, and incredibly expanded mental capacity (as demonstrated consistently throughout the novel, V is a genius in the fields of explosives, martial arts, philosophy, literature, politics, hacking, music, chemistry, and, as stated by Dr. Surridge in the graphic novel, gardening).
Over time, the man is allowed to grow roses (violet carsons) and raise crops for camp officials. The man eventually starts taking surplus ammonia-based fertilizer back to his cell, arranges it in bizarre, intricate patterns on the floor. He then takes a large amount of grease solvent from the gardens. In secret, the man uses the fertilizer and solvent to make mustard gas and napalm. On a stormy night (Nov. 5th), he detonates his homemade bomb and escapes his cell. Much of the camp is set ablaze, and many of the guards who rush in to see what happened are killed by the mustard gas. The camp is evacuated and closed down. He adopts the new identity, "V", and dons a Guy Fawkes mask and costume. V then spends the next five years planning his revenge on the fascist government, building his secret base, which he calls the "Shadow Gallery". He then kills off most of the over 40 surviving personnel from Larkhill, making each killing look like an accident. He saves Prothero, Lilliman and Surridge, (the three most responsible for the experiments on him) for last, showing the remorseful Surridge a merciful consideration by poisoning her in her sleep.
Four years after his escape from Larkhill, V blows up Parliament on November 5, Guy Fawkes Day. V then kidnaps Prothero, who is now the "Voice of Fate" on the government's propaganda radio, and drives him insane by destroying his prize doll collection in a satire of the exterminations that occurred at Larkhill. V kills now-Bishop Lilliman by forcing him to eat a communion wafer laced with cyanide. Norsefire had infused a perversion of religion into their rhetoric, saying that those who were exterminated were not pure in the eyes of God, and V's black humor was enforcing Lilliman to put some of his religious rhetoric to the test of transubstantiation. V then kills Surridge, the one Larkhill official who feels remorse for her actions, by injecting her with a poison that painlessly kills her. Having thus killed his personal foes, V moves his plans forward.
V stages an attack on the government's propaganda broadcasting station, strapping himself with explosives and forcing the staff to follow his orders under threat of detonating them. V then broadcasts a message to the people, telling them to take responsibility for themselves and rise up against their government. Finally, V destroys the government's CCTV surveillance buildings, eroding its control over British citizens. However, V is mortally wounded when he is shot by Finch, and he staggers back to the Shadow Gallery, where he dies in Evey's arms. Evey then puts him in state, surrounded by violet carsons, lilies and gelignite, in an Underground train that stops at a blockage along the tracks right under 10 Downing Street, where the explosives-laden train detonates, giving V a Viking funeral, fulfilling his final request to her in the process. Evey then takes on the mantle of "V."
V's true identity is a mystery, and he visibly removes his mask only once during the entire story (at Surridge's request), at which point his back is to the reader. Surridge tells him "it is beautiful", in contrast to her personal notes, where she mentions that the man in cell V was ugly although she mentions "Physically, there doesn't seem to be anything wrong with him. No cellular anomalies, nothing".
He doesn't even consider "V" his "name", saying "I do not have a name. You can call me V". The only explanation given regarding V's past is Surridge's diary, which V leaves out in the open for the "Finger" (Norsefire's secret police) to find after he kills her. Eric Finch, the head of the "Nose" (the Party's detective division) and one of Norsefire's most powerful officials, reads through the diary, but points out that V wanted them to read it. V also tore out many pages, which possibly left clues to his true identity before arriving at the camp. Finch further speculates that V fabricated the version of Surridge's diary, which he left with her body, just to confuse the police.
His confidante Evey Hammond speculates that V might be her own father, who was arrested years before as a political prisoner; V denies it.
As Finch comments on the pages V tore from Surridge's diary "What was on the missing pages, eh? His name? His age? Whether he was Jewish, or homosexual, or black, or white?" He later proclaims to Finch that he is "an idea."
Upon witnessing V's death, Evey declines to unmask him with the conviction that even if he was her father, learning the man's true identity would not be worth diminishing what he endeavored to symbolize. Eventually, Evey takes over V's persona and his mission to consider herself as anarchy incarnate.
The 2006 film adaptation of the graphic novel starred Hugo Weaving as V.
In the film, V is a freedom fighter rather than an anarchist terrorist. He is disfigured (a result of burns) instead of being described as being ugly. His physical abilities are unexpected results of myriad experiments performed on many if not all of Larkhill's detainees (apparently, only V got any benefit from the gruesome experiments). At the end of the film, he says that he has fallen in love with Evey.
There are several plot deviations. In the film, he only bombs the Old Bailey and Houses of Parliament building. It is Peter Creedy who is the main antagonist and confronts V at the end, instead of Finch. Creedy shoots Sutler (Adam Susan in the graphic novel), but V refuses to take off his mask, and Creedy and his men shoot V. V wore a breastplate to deflect the bullets but was still mortally wounded. He dies in Evey's arms. Finch then confronts Evey, but puts down his weapon after learning about the corruption of the Norsefire regime and joins Evey as they watch V's bomb destroy the Houses of Parliament.
According to Moore, he was designed to be the protagonist, so that readers could decide for themselves whether he was a hero fighting for a cause, or simply insane.
Moore has confirmed that V is not Evey's father.