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

Harry Potter and the Order of the Phoenix is the longest Harry Potter book in the original English series by word count.

Published in 2003, the fifth novel contains roughly 257,000 words in its English edition. It is notably longer than the other six books, including Harry Potter and the Goblet of Fire, which is the second-longest main-series volume by common word-count estimates.

The story introduces the Order of the Phoenix as an organised resistance against Voldemort’s return. Harry also faces the Ministry of Magic’s denial campaign, the authoritarian Hogwarts regime of Dolores Umbridge, and the emotional strain of adolescence and wartime uncertainty.

Page totals vary between editions because of typography, paper size, illustrations, and language. That is why word count is the clearest basis for this comparison. Translations can also differ substantially in length, so the answer refers specifically to the original English text.