Which Harry Potter book by J.K. Rowling is the longest by word count in the UK edition?

Harry Potter and the Order of the Phoenix is the longest Harry Potter book by word count in the UK edition.

Published in 2003, Harry Potter and the Order of the Phoenix has about 257,000 words in its British edition, making it the longest volume in the seven-book series by commonly cited word counts. It follows Harry’s fifth year at Hogwarts and the growing conflict with the returning Lord Voldemort.

The novel introduces Dolores Umbridge as Hogwarts’ High Inquisitor and develops the student group known as Dumbledore’s Army. It also explores the Ministry of Magic’s refusal to accept that Voldemort has returned.

Page totals can vary between editions because of typography, formatting, and language. The word-count comparison is therefore more useful than a page-count comparison, especially between British and American editions.