The Duchess is a 2008 historical drama film directed by Saul Dibb, who co-wrote the screenplay with Jeffrey Hatcher and Anders Thomas Jensen, based on the 1998 book Georgiana, Duchess of Devonshire by Amanda Foreman, about the late 18th-century English aristocrat Georgiana Cavendish, Duchess of Devonshire. She was a distant relation of Diana, Princess of Wales, where the quote "There were three people in her marriage" in the promotional poster comes from. The Duchess was the older sister of Lady Diana's great-great-great-grandfather, George Spencer, 2nd Earl Spencer.

The Duchess was released on 5 September 2008 in the United Kingdom. The film received generally positive reviews from critics. It won the Best Costume Design and was nominated for Best Art Direction at the 81st Academy Awards.