Age: 17 (first season), 18 (second season)
Date of Birth: December 5, 2000 a.t.b. (Sagittarius)
Blood Type: A
Height: 178-183 cm
Weight: 56 kg
Occupation: Ashford Academy Student
Known Relatives: Charles zi Britannia (father), Marianne vi Britannia (mother, deceased), Nunnally vi Britannia (little sister)
Allegiance: Order of the Black Knights
Position: Order of the Black Knights Leader
Knightmare Frame: Burai, Gawain, Shinkiro
Favourite quote: The only ones who should kill, are those who are prepared to be killed.
Lelouch is introduced in the first episode of the series as a student of Ashford Academy high school, where he is a member of its student council. A brilliant thinker who is quite talented at chess, he lives with his younger sister, Nunnally, with their maid, Sayoko Shinozaki, at a house situated within the compounds of Ashford Academy, where they are looked after by the Ashford family.
Lelouch is soon swept into the conflict between the Britannia Empire and the pockets of resistance which oppose it when he accidentally boards a truck being used by Japanese resistance operatives. Within the truck is a capsule holding C.C., who sacrifices herself to save him from the military forces trying to recapture her. When it seems as if her sacrifice was pointless, C.C. suddenly touches his hand and offers him the "Power of the King," the mythical power of Geass. The Geass manifests itself in him as the power of absolute obedience, which allows him to make people obey his orders without question.
With his new power, Lelouch begins his rebellion against the Empire, forming the Order of the Black Knights and takes up the identity of Zero to lead them, becoming a revolutionary and gaining popular support amongst the people.
Lelouch's Geass, given to him by C.C., grants him "the power of absolute obedience," allowing him to plant commands within a person's mind upon eye contact which they will obey without question. Activation of his Geass is visually represented by the manifestation of a Geass sigil in his left eye. Commands dictated in this state are written into the minds of the designated targets once the sigil projects from his eye to theirs. Lelouch could initially toggle Geass activation at will, but subsequently loses this control to an affliction known as Geass runaway.
Of all the Geass abilities in the series, Lelouch's has been explored the most, and also seems to have the most restrictions and side effects of any Geass introduced.
* Commands must be issued verbally.
* The victim must make direct eye contact for commands to be issued. The maximum effective distance is 270 meters. Line of sight via a reflective surface is sufficient for the effect to occur.
* Commands may be issued only once to any given individual, but any number of commands may be issued at initial application so long as eye contact is unbroken. Since Jeremiah's Geass Canceller negates all Geass effects, those exposed to it may be commanded once again.
* The victim will not perform any action disallowed by their physical or mental capabilities, though they will try to carry out the command to the best of their ability. For example, a victim will not be able to correctly answer a question they don't know the answer to, but will direct the user to someone who can if they are able. However, commands that affect the mind or consciousness, such as telling the victim to forget something, will take effect despite the fact that the victim could not normally force themselves to do so.
* An action will be carried out for as long as dictated in its command, or upon the indicated conditional circumstance. Eye contact does not need to be maintained for command execution to occur. No upper limit has been established, but the conditional command Lelouch gives Suzaku is still in effect more than a year later.
* The victim's memories for the duration of command issue and execution are sealed and cannot be recalled.
* A victim may resist a commanded action to some degree if it is utterly repugnant to them.
So long as the above conditions are met, commands may be issued to anybody besides those who have gained the power of immortality and to any number of individuals at once. Those under the effect of Geass have a red outline on their pupils, presumably a visual cue for the viewer since the characters never point it out.
Even without his Geass, Lelouch is a formidable opponent. He is highly intelligent, possessing a genius-level intellect, and is capable of devising and executing strategies with incredible speed and precision. Rolo notes that operating the Absolute Defense Territory of the Shinkirō requires complex calculations which he cannot perform, while Lelouch almost makes it look easy. In the audio dramas, Suzaku says that, when they were children, Lelouch devised a secret sign language containing over 500 words.
Lelouch is quick to deduce facts from simple clues. In episode 14, when Mao says C.C.'s name, Lelouch instantly comes up with fourteen different possibilities for Mao's identity, including the correct one. Lelouch is also able to predict the Lancelot's actions exactly through his study of their past battles, allowing Kallen and the Four Holy Swords to almost defeat it (only Suzaku's reflexes saved his life).
Lelouch is also charismatic and persuasive; as Zero, he is able to win the support of much of Japan's population through well-delivered speeches combined with his ability to make miracles in almost any situation through his superior tactical planning. Mao repeatedly praises Lelouch's persuasive talent, and V.V. remarks that Lelouch is "a lot like his father."
Physically, Lelouch is underwhelming. He possesses the physical prowess of a teenager who engages in little to no strenuous physical activity. Thus, one of Lelouch's traits is the inability to run very fast or for any substantial period of time. Within the series, this is usually played for comedic effect, as Lelouch is constantly outpaced by his classmates in every situation, and even the most simple tasks requiring manual labor exhaust him before he manages to accomplish anything significant. This joke is taken to its logical conclusion in the second season, where it is revealed that Lelouch is supposed to attend remedial physical education classes, but skips them as often as possible. This creates problems when Sayoko poses as Lelouch: she is a master of martial arts, and hence far more athletic than Lelouch himself. Lelouch laments the problem and decides to have Sayoko attend his gym classes to fix it.
Lelouch is also shown to be very talented at most domestic skills, including cooking and sewing; it has been stated that this comes as a result of his taking care of himself and Nunnally for seven years. He has been shown to be an excellent cook, and is usually the one cooking the food for parties held by the Student Council, both because the others (except Milly) are terrible cooks and nobody else can meet his exacting requirements (such as measuring ingredients to three significant decimals).
Lelouch also has some skill with firearms, usually brandishing a Britannian pistol when threatening someone. His Knightmare piloting skill has been shown to be proficient but not exceptional; he is a capable pilot by himself, though he tends to be overwhelmed by Suzaku and other pilots with more advanced Knightmares at their disposal. When Lelouch pilots a standard Knightmare on the battlefield, he is typically accompanied by Kallen, who is an elite Knightmare pilot and the leader of his personal squad, Squad Zero.