The Princess Diaries is a 2001 American coming-of-age comedy film produced by Walt Disney Pictures, directed by Garry Marshall, and written by Gina Wendkos. Based on Meg Cabot's 2000 young adult novel of the same name, it stars Anne Hathaway (in her film debut) and Julie Andrews, with a supporting cast consisting of Héctor Elizondo, Heather Matarazzo, Mandy Moore, Caroline Goodall, and Robert Schwartzman. The plot follows Mia Thermopolis (Hathaway), a shy American teenager who discovers she is heir to the throne of a European kingdom. Under the tutelage of her estranged grandmother (Andrews), the kingdom's reigning queen, Mia must choose whether to claim or renounce the title she has inherited.

Feeling confident about the novel's film potential, Cabot's agent pursued producer Debra Martin Chase about adapting The Princess Diaries into a feature-length film, an idea she pitched to Disney upon reading the book. After obtaining the film rights, Disney originally greenlit the project under the title The Princess of Tribeca, reverting it once its setting was changed from New York to San Francisco, where the majority of the film was shot between September and December 2000. Marshall agreed to direct because he found the story ideal for family entertainment. Despite having little involvement in the film's development, Cabot was consulted about various changes to its story and characters. Hathaway won the lead role over several established young actresses in her motion picture debut, while The Princess Diaries commemorated the end of Andrews's semi-retirement from acting and return to Disney films, her first since Mary Poppins (1964).

The Princess Diaries premiered at the El Capitan Theatre in Los Angeles on July 29, 2001, and was theatrically released in the United States on August 3. The film was an unexpected commercial success, grossing over $165 million worldwide, despite receiving mixed reviews for its plot, themes, and Hathaway's performance. Ranking among the most profitable films of 2001, The Princess Diaries defied industry expectations as pundits had expected the film to underperform due to its G rating and subject matter. The film's success is credited with establishing Hathaway as a bankable actress and reviving Andrews's film career. A sequel, The Princess Diaries 2: Royal Engagement, was released in 2004, and a third installment has been in development.