Which Harry Potter film was the only one not written by screenwriter Steve Kloves?

Harry Potter and the Order of the Phoenix was the only Harry Potter film not written by Steve Kloves.

The screenplay was written by Michael Goldenberg for the 2007 film directed by David Yates. It adapts J.K. Rowling’s fifth novel, in which Harry returns to Hogwarts amid official denial that Voldemort has returned and faces the authoritarian teacher Dolores Umbridge.

Steve Kloves wrote the screenplays for the other seven films in the main Harry Potter film series. His long involvement helped maintain continuity across adaptations, while Goldenberg handled the screenplay for Order of the Phoenix.

The film is also notable as the first Harry Potter movie directed by Yates, who later directed the remaining three main-series films. Rowling was involved as a producer on the film, but screenwriting credit belongs to Goldenberg, not Rowling or Kloves.