Which Harry Potter book is the longest in the original English series by word count?

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

Published in 2003, it contains more text than any of the other six novels in the series. The story follows Harry’s fifth year at Hogwarts, the Ministry of Magic’s refusal to accept that Lord Voldemort has returned, and the formation of Dumbledore’s Army.

The book is also notable for introducing Dolores Umbridge as a major antagonist and for expanding the political conflict beyond the school. Its length is often discussed alongside its darker tone and multiple storylines.

Page counts are less reliable for comparisons because editions use different type sizes, page dimensions, and layouts. Word-count comparisons therefore provide a clearer basis for calling Order of the Phoenix the longest original English volume. Translated editions can have different lengths because languages do not use the same number of words.