Nunnally Lamperouge, originally born Nunnally vi Britannia, is the younger sister of Lelouch vi Britannia and a central supporting figure in Code Geass: Lelouch of the Rebellion R2. She is a princess of the Holy Britannian Empire, born on October 25 to Emperor Charles zi Britannia and Marianne vi Britannia, and was 87th in line to the imperial throne. When her mother was assassinated, Nunnally was caught in the attack and lost the use of her legs. Her blindness was initially believed to be psychological trauma from witnessing the murder, but it was later revealed that her father had placed a Geass on her that sealed her sight as a form of protection. Afterward, Nunnally and Lelouch were exiled to Japan as political prisoners, where she first met Suzaku Kururugi. Following the Britannian invasion of Japan, the siblings adopted the surname Lamperouge and were sheltered by the Ashford family, with Nunnally attending Ashford Academy while using a wheelchair and relying on others for daily care.

Nunnally is characterized by extraordinary kindness, patience, and empathy. She endures her blindness and paralysis with a consistent smile and warmth, and Lelouch observes that her smile is an expression of gratitude, born from her dependence on the kindness of others. In private during childhood, she was prone to tantrums, but by the time of the main story she is gentle, forgiving, and deeply concerned with the well-being of those around her. She holds a peaceful, idealistic worldview and believes that the world can be changed through gentle means rather than force. Despite her soft nature, she is capable of making difficult and even severe decisions when she believes they are necessary. One of her notable traits is an ability to sense when someone is lying simply by holding their hand.

Her central motivation is to create a peaceful world, and she serves as the primary inspiration for Lelouch's rebellion against the Britannian Empire. In R2, she carries on the will of her late half-sister Euphemia li Britannia by seeking to revive the Special Administrative Region of Japan, working alongside Suzaku despite the fact that Lelouch, as Zero, is publicly condemned as a traitor. After being abducted by V.V. near the end of the first season, her very existence is erased from the memories of those who knew her, including Lelouch, and Rolo Lamperouge takes her place as Lelouch's supposed younger brother. She reappears in R2 as the new Viceroy of Area 11, the final person to hold that office. In this role, she shows political awareness and moral firmness, confronting subordinates over policies that would burden the Japanese population and insisting that plans be rewritten to avoid unnecessary harm. She also shows compassion to Kallen Stadtfeld, arranging better treatment for the captured pilot and speaking with her about Lelouch.

During the Second Battle of Tokyo, Nunnally is seemingly killed when the F.L.E.I.J.A. bomb is detonated, but she survives by taking a different ship. She next appears on the Damocles, the floating fortress controlled by Schneizel el Britannia, who presents her as the rightful heir to the throne while manipulating her for his own purposes. Believing Lelouch's actions have made him a tyrant, Nunnally declares herself his enemy and insists on being given the F.L.E.I.J.A. launch controls so that she can personally atone for his sins. She is disturbed by how easily she can order the destruction of his forces. During Lelouch's assault on the Damocles, she is thrown from her wheelchair while searching for the launch key, and in that moment she breaks her father's Geass through her own willpower, restoring her sight. When Lelouch arrives and asks for the key, Nunnally opens her eyes and challenges him, revealing that she intends to turn the Damocles into a worldwide symbol of hatred to unite humanity, a plan nearly identical to his own. Lelouch hesitates but ultimately uses his Geass to force her to surrender the key, telling her that he loves her. Because she is unaware of these words while under the Geass, she calls him a demon as he leaves. In the aftermath, she is taken prisoner and forced to witness Lelouch's execution, where Suzaku, disguised as Zero, kills him before her eyes. After learning of the true purpose behind Lelouch's sacrifice, Nunnally dedicates herself to preserving peace, serving as an honorary advisor to the World Humanitarian Organization in later years.

Her most important relationship is with her brother Lelouch. The two share deep mutual affection, and Nunnally states that she loves him more than anyone else. She is the emotional core of his goals, and her safety and happiness shape nearly every major decision he makes, even when their paths place them in direct opposition. Her relationship with Suzaku is one of close friendship and trust, though it becomes strained when he becomes a Knight of the Round and she realizes he is not being honest with her. She reveres Euphemia and treats her legacy as a guiding purpose. Her father, Charles, is a distant and cold figure whose Geass both shielded and burdened her, and Schneizel exploits her for political ends while she remains largely unaware of his manipulation. Her primary caretaker is Sayoko Shinozaki.

Nunnally possesses no combat abilities or supernatural powers. Her strengths are emotional intelligence, an ability to perceive deception through physical contact, strong moral will, and the capacity to inspire loyalty and hope in others. She also demonstrates political judgment during her time as Viceroy, and despite being blind, she continues to enjoy drawing from memory. Her development across R2 traces her transformation from a sheltered and dependent figure into a political authority who is forced to confront her brother, and finally into a survivor devoted to carrying forward the peaceful world he died to create.