Claim: Anne Hathaway played Mia Thermopolis.

The Princess Diaries is a 2001 American comedy film directed by Garry Marshall and written by Gina Wendkos , based on Meg Cabot 's 2000 novel of the same name . It stars Anne Hathaway -LRB- in her film debut -RRB- as Mia Thermopolis , a teenager who discovers that she is the heir to the throne of the fictional Kingdom of Genovia , ruled by her grandmother Queen Dowager Clarisse Renaldi -LRB- Julie Andrews -RRB- . The film also stars Heather Matarazzo , Héctor Elizondo , Mandy Moore , and Robert Schwartzman .   Released in North America on August 3 , 2001 and was a commercial success , grossing $ 165.3 million worldwide . The film was followed by a sequel , The Princess Diaries 2 : Royal Engagement , released in August 2004 .