Which J.K. Rowling novel is the longest of the original seven Harry Potter books?

Harry Potter and the Order of the Phoenix is the longest novel in the original Harry Potter series.

The fifth book was published in 2003 and contains more than 250,000 words in its English edition, making it substantially longer than the other six novels. It follows Harry’s fifth year at Hogwarts and introduces the authoritarian Ministry-appointed professor Dolores Umbridge.

The title refers to the revived Order of the Phoenix, a secret group opposing Lord Voldemort. The novel also develops the political denial surrounding Voldemort’s return and Harry’s difficult connection to the prophecy.

Readers sometimes confuse the longest book with the longest film. The film adaptation is not the longest movie in the series; its screenplay necessarily omits many subplots and scenes from the much larger novel.