File:Chara 21.jpg Cornelia li Britannia 27 years old (28 at R2), (コーネリア・リ・ブリタニア, Kōneria Ri Buritania) is the second princess of the Britannian Imperial Family and is Lelouch's half-sister. She is extremely skilled in Knightmare Frame combat and completed the establishment of Area 18 shortly before arriving in Area 11. She is voiced by Junko Minagawa (Japanese), Mary Elizabeth McGlynn (English).
Cornelia, is the Chief General of the Imperial Army and goes to Area 11 to apprehend Clovis's murderer, the mysterious Zero, as well as avenging Lelouch and Nunnally (unaware of the fact that they survived their predicament as political hostages) by putting an end to the conflict there. This loss of the three siblings seems to be the source of her distrust toward foreigners and Honorary Britannians. She pilots a customized Gloucester Knightmare Frame and has her own circle of devoted officers. After Clovis' death, Cornelia becomes the new Governor-General of Area 11.
As a child, she appeared to have doted upon her younger sister Euphemia; as a result, Euphemia is Cornelia's only known weak spot. Clovis believes that she and Prince Schneizel know about the truth regarding the murder of Marianne vi Britannia, although Euphemia later tells Lelouch that Cornelia has long idolized Marianne and conducted investigations on the murder.
Cornelia first appears in episode five, having established Area 18 before entering Area 11 with the intention of apprehending the murderer of her brother, Clovis. She subsequently appears in several battles against Zero, unaware that he is Lelouch, and intends to capture him and bring him to justice.
Worried about her younger sister, Cornelia persuades Euphemia to take on a personal Knight. Though Euphemia eventually agrees, Cornelia remains concerned when Euphemia selects honorary Britannian Suzaku Kururugi. Cornelia's concerns regarding Euphemia's safety only increase when Euphemia proposes and establishes the Special Administrative Region of Japan, a plan which Cornelia personally opposes but allows Euphemia to proceed with.
Following Euphemia's death, Cornelia vows to take down Zero during the Black Knights' first open attack on Tokyo. She almost succeeds, outmanuvering and repeatedly scoring hits on Zero's supposedly superior Gawain unit, before Darlton, under the influence of Lelouch's Geass disables her Gloucester and wounds her. Lelouch initially plans to use her as a hostage to force the opposing Britannian military to surrender but is thwarted by Jeremiah Gottwald.
Instead, Lelouch reveals his identity to Cornelia, who realizes that, since Lelouch is actually alive, Zero's actions were motivated entirely for the sake of Nunnally. However, she cannot accept that Clovis and Euphemia had to die as a result. Before Cornelia can argue with Lelouch, he uses his Geass on her in order to interrogate her about the day his mother, Marianne, was killed. Cornelia reveals that though she was the head of the security at the palace where Marianne was that day, Cornelia had been ordered by Marianne herself to remove the palace's defences. Unable to comprehend why Marianne would do such a thing, Lelouch continues to press Cornelia for information; his sister is unable to provide him with any other details save that their brother Schneizel El Britannia was the one who took Marianne's body away.
Lelouch flees soon afterward to save Nunnally, who has been abducted, and the injuried Cornelia summons Suzaku to her side. As a possible indication of change in her attitude of distrusting Honorary Britannians, she grants him the officially-recognized noble title of a knight. Since she also asks him to suppress the news of her injury.
Gilbert G.P. Guilford and her knights are waiting in Area 11 for her return. In season 2 she returns as a rogue, seeking the cause of Geass and those who killed her brother and sister. She seeks to expose them to the world to prove her sister's innocence. She discovers the location where V.V. and Jeremiah Gottwald have made their base and confronts General Bartley. He unexpectedly asks her for help in escaping, believing that the Emperor's goal could bring about the end of the world, but is captured by V.V. During the Black Knights' assault on the Directorate, she escapes and uses a damaged Akatsuki (rigged with numerous weapons from other Akatsuki units) to attack V.V.'s Siegfried, damaging it and allowing her to deliver the finishing blow in tandem with Lelouch. Jeremiah saves her from being crushed by the plummeting Siegfried and brings her before Lelouch. She is held prisoner by the Black Knights, but manages to escape during the second battle of Tokyo and joins Schneizel when he arrives as an envoy. She reveals everything she learned while investigating the Geass Directorate to him. When Schneizel announces his intention to usurp the throne, Cornelia is reluctant but doesn't object. She later joins Schneizel and his faction after Lelouch became the Emperor.
When she learns of his plan to position Damocles in such a way that it could strike all over the world at the same time, she tries to stop him, only to be gunned down. She is later shown in a hospital bed, recovering. Two months later, after the culmination of Lelouch's plans (the Zero Requiem), she is shown leading a small resistance group (including Villetta and Guilford). They take advantage of Lelouch's assassination to restore order. She is last seen in a photo alongside Guilford, at Ohgi and Villetta's wedding.