Date of Birth: November 22, 1979 a.t.b.

Nationality: Britannian

Blood type: B

Age: 30 (at the time of her "death"), 39 (at R2)

Date of Death: 2018 a.t.b. (2009 at the time of her "death")

Marianne Vi Britannia was the 5th wife of the Emperor of Britannia and the mother of Lelouch and Nunnally. The surname Lamperouge presently assumed by Lelouch was her maiden name. Her commoner status by birth caused her to earn the jealousy of other imperial wives and nobles, which Lelouch suspects had resulted in her murder. Lelouch's investigation revealed, however, that several members of the Imperial House not related to her by blood respected and admired Empress Marianne, such as Clovis, Euphemia, especially Cornelia, who idolized her and put a lot of fruitless effort into investigating the assassination.

It is hinted that her supporters were the Ashford family, which explains why their social statuses were ruined after her death and why they consented to protect Lelouch and Nunnally. She had also piloted one of the earliest Knightmare Frames, the Ganymede, which was developed by the Ashford family and is well known for her superior Knightmare Frame piloting skills, hence the nickname, "Marianne the Flash." In episode 23, it is revealed that C.C has apparently been talking to Marianne herself, via an unknown method. In episode 7 of R2, C.C. was talking with Marianne again.

At the end of season one,