Mia Thermopolis

Amelia Mignonette Grimaldi Thermopolis Renaldo, Crown Princess of Genovia (named Amelia Mignonette Thermopolis Renaldi in the film series), commonly known as Mia Thermopolis, is a fictional character and the protagonist of The Princess Diaries novels by Meg Cabot. The story revolves around her diary, which she writes in religiously, and her relationships with her best friend Lilly Moscovitz, her long-time boyfriend and "the love of her life" Michael Moscovitz, her grandmother, and others. She is the princess of fictional country Genovia, having been pushed into the title, being the sole heir.

Mia lives in a loft in New York City, with her mother, Helen Thermopolis, and her ginger cat, Fat Louie. Helen begins dating Mia's algebra teacher, Frank Gianini, during Mia's freshman year, and as the series develops Helen and Frank get married and have a child together. During the year she attends Albert Einstein High School, and spends her holidays in Miragnac, a castle in Genovia.