Chi (Japanese: ちぃ, Hepburn: Chii), "née" Elda (Japanese: エルダ, Hepburn: Eruda), is a fictional character in the manga series Chobits and its anime adaptation. Chi is a Chobit, a type of personal computer called a persocom that is far more technologically advanced than regular persocoms, and who are said to possess true machine intelligence rather than relying on software programs like other persocoms. She is found by Hideki, a high school graduate who has no idea about her unique abilities or of her past. Over the course of the series Hideki tries to discover what type of persocom Chi is, being told that she is something special. He finds her a job, and has to deal with her being kidnapped at one point. Chi learns about the things around her and what it means to be in love. At the end of the series, Chi finds the person "just for her", and her forgotten identity is revealed, causing Hideki to confront his feelings.

In two interviews describing the series Chi's creators, Clamp, said it would be much easier if computers could speak to you when they had errors. Chi is voiced by Rie Tanaka in the anime and Michelle Ruff in its English dub (credited as Georgette Rose). The manga and anime follow Hideki's find of Chi and their relationship, but differ in the storyline. Chi's critical reception has been mostly positive, with reviewers calling her "cute". In addition to Chobits, she is also a crossover character in the series Tsubasa: Reservoir Chronicle and is referenced in other works.

In an interview when describing Chi's character, Clamp member Satsuki Igarashi stated "Lately we've been saying that the easiest to understand is Chii from 'Chobits.' Errors occur with computers. Things like 'Although it's fine to speak the instructions' and 'Please fix this problem here' might be spoken in a cute voice." In addition, an explanation for Chobits's plot was given by Igarashi who stated: "The only thing our computer at the time would say was “Error, Error”. It never told us, or gave the slightest clue, as to what was the matter." Clamp also describes Chobits as a variation of the "boy living with mysterious girl" genre. Chi's design as a personal computer resulted from Ohkawa's wish to increase the sense of "emotional discomfort" around becoming emotionally involved with something considered to be merely a lifeless machine.

The name "Chobi", came from the name of a cat at the place of Nekoi's former employment, which the group made into "Chobits", as the characters Elda and Freya were twins. In the series, Clamp had Chi's creator, Ichiro Mihara (a character from their shared universe work Angelic Layer), use the word "Chobi" to describe anything he thought was "small and hopelessly adorable"; two Chobi (the sisters Elda and Freya) become "Chobits".

Chi first appears atop a trash pile in an alley where she is found by Hideki Motosuwa, a high school graduate who knows very little about computers or the androids known as "persocoms" (personal computers) that have become the fashionable item to have in the city. Unlike other persocoms, her activation switch is located in an unusual place: her crotch. She has difficulty communicating with Hideki at first; the only word that she says is "chi", which becomes her given name, but slowly she learns how to speak. Having no memory of her past life, she is taught by Hideki to perform simple tasks. Hideki's neighbor Shinbo and computer prodigy Minoru determine that Chi is no ordinary persocom, and may be a legendary "Chobit", possessing synthetic intelligence.

At one point Hideki considers having to take on a second job due to his poor financial state. He is eventually able to convince his former employer Hiroyasu Ueda to hire Chi at his bakery during his anniversary sale. Chi eventually finds herself kidnapped by Yoshiyuki Kojima. Yoshiyuki initiates a program that he had created especially for Chi, which is designed to break through her firewalls, and when he embraces and gropes her, Freya intervenes by binding him with wires connected to Chi and releasing a powerful, concussive blast. Hideki and Shinbo find her, and Freya vanishes, causing Chi to collapse from the energy used. She recovers and briefly reunites with Hideki, before losing consciousness. Shinbo then forces Yoshiyuki to transfer his persocom Kotoko's registration to Hideki to prevent Yoshiyuki from deleting her memories, so that a record of his kidnapping exists.

Hideki later learns that before he found Chi, her name was Elda. After Ichiro's wife, Chitose Hibiya, noticed that Freya—the first Chobit who was created to be the daughter she and her husband could never have—was becoming increasingly depressed as time went by, Elda was created to be her younger sister to cheer her up. Freya, however, had fallen in love with Ichiro, and the emotional pain of her unrequited love and her wish to not disturb her parents' happiness eventually caused her to severely malfunction. Elda took Freya's program, which included her mind and memories, into herself to preserve her memory. Before losing her own memories as a result of her actions, Elda requested to be left alone outside, away from her family, so that she would not have the possibility of suffering the same fate as her sister. Her father then gifted her with a program which will delete the recognition programs of all persocoms if she fails to find her soulmate, while her mother authored the children's book series A City with No People, a story within a story about the relationships between persocoms and people, to help Chi in her quest.

Towards the end of the series, Zima and Dita, persocom agents for the Japanese government who know the outcome of Chi's special program, arrive at Hideki's apartment. A minor scuffle ensues between Dita and Chi, before Zima restrains Dita, wishing to see the outcome of Hideki's decision and ultimately too falling under Chi's influence. Hideki confirms his love for Chi, only to find that Freya has taken control of her body. Learning that he can never engage in sexual intercourse with Chi without rebooting her systems, erasing everything that makes her a unique individual, Hideki states that he will love Chi regardless. Freya confirms that while Chi and herself are indeed the legendary Chobits, they possess neither sentience nor emotions, but rely on software programs just like every persocom. Again, Hideki stands by his love for Chi. Hideki declines her offer to tell him about Chi's special ability, and Freya vanishes after imploring him to take care of her sister. Chi awakens, embracing Hideki. The series ends with Chi holding Hideki's hand with visible rings Chi had chosen for the two of them.