The Princess Diaries

Amelia Mignonette Grimaldi Thermopolis Renaldo (Amelia Mignonette Thermopolis Renaldi in the Movies), Princess of Genovia is the protagonist of the series. She is the daughter of Helen Thermopolis, a painter, and Philippe Renaldo, the crown prince of Genovia. Mia is also the current Princess Regent of Genovia.

Mia is sometimes shy and has a down-to-earth personality, though on occasion Mia shows herself to be quite sarcastic and sly. Throughout the series she is very self-critical of herself, describing herself as flat-chested, taller than most girls at 5-foot-9, and with embarrassingly large feet. She also has a tendency to over-analyze things and worry too much.

In Disney's The Princess Diaries 2001, Mia (who was portrayed by Anne Hathaway) is aged 15, unlicensed, and owns a 1965 Mustang. She has similar qualities, but her father dies two months prior to where the movie begins, and her last name is Renaldi instead of Renaldo. She lives in San Francisco instead of New York.

Clarisse Maria was formally known as Clarisse Marie Grimaldi Renaldo, Dowager Princess of Genovia.

Clarisse is the dowager princess of Genovia and Mia's paternal grandmother. Mia refers to her as "Grand-mère" (French for "Grandmother"). As a young woman, she married Prince Rupert Renaldi and had two sons. She speaks French most of the time, but she can also speak English; however, she disdains English as a vulgar language. She is almost always accompanied by her miniature poodle, Rommel, who is notable for having a severe case of OCD that causes him to lick his own fur off. She smokes often and enjoys drinking sidecars. She is not hesitant about lying or manipulating others in order to get her own way.

Mia's best friend since kindergarten, Lilly is a highly intelligent and opinionated person who has her own public-access television show, titled Lilly Tells It Like It Is, in which she discusses political and social issues. By the end of the series, her TV show is picked up by a network and is apparently very popular in South Korea. Lilly is not considered to be very pretty; Mia often describes her face as being "squashed in like a pug's". However, she has a well-developed figure.

In the 2001 Disney Movie, Lilly, portrayed by Heather Matarazzo, is portrayed as intelligent, confident, and socially conscious. Her talk show is called "Shut Up and Listen". She is then a student at Berkeley. In The Princess Diaries 2: Royal Engagement, Mia appoints Lilly as her royal secretary.

Lilly's older brother, and Mia's main love interest throughout the series. Michael has brown eyes and thick, dark hair and is tall. Mia insists that he is the third best-looking guy at AEHS after Josh Richter and Justin Baxendale and describes his nose as aquiline, mouth as "eminently kissable", and neck as aromatic due to an intoxicating blend of Tide from his shirt collar, his Gillette shaving foam, and Ivory soap. Though he often clashes with his younger sister, Michael and Lilly are in fact close siblings and friends. He used to run his own webzine, Crackhead, but had to disband it after an editorial stating the merits of Linux over Windows, which caused a loss of advertisers and funds. Shortly after this, Michael starts a band called Skinner Box (a name suggested by Mia) with a few friends, including Boris Pelkowski.

A student at AEHS, Tina is the daughter of a Saudi Arabian oil sheik and a British former supermodel. Because of her father's status, she has to have the protection of a bodyguard, Wahim, which isolates her from the other students until Mia sits with her after a fight with Lilly in the first novel.

• Lars van der Hooten: Mia's very protective Swedish bodyguard.
• Helen Thermopolis: Mia's mother. She has a career as an artist and spends most of her time in her studio.
• Frank Gianini: Mia's algebra and homeroom teacher. He dates her mother, Helen, and marries her when she becomes pregnant with Mia's half-brother, Rocky.
• John Paul "J.P." Reynolds Abernathy IV: Initially known as "The Guy Who Hates It When They Put Corn In the Chili", J.P. meets Mia via Grand-mère's school musical in Party Princess.
• Boris Pelkowski: A Russian violin virtuoso, and Lilly's boyfriend. His habits include tucking his sweater into his pants, breathing through his mouth, and playing the violin in Gifted and Talented class, when everyone else wants him to be quiet.
• Josh Richter: Lana Weinberger's boyfriend. He is on the crew team and is co-valedictorian.
• Lana Weinberger: A popular junior cheerleader with long blonde hair, a peaches-and-cream complexion, baby blue eyes and a voluptuous figure