Which Harry Potter book is the longest in the original English editions written by J.K. Rowling?

Harry Potter and the Order of the Phoenix is the longest Harry Potter book in the original English editions written by J.K. Rowling.

Published in 2003, the fifth novel contains 766 pages in its United Kingdom hardcover edition and 870 pages in its United States hardcover edition. Page totals differ by edition because of formatting, paper size, and publishing design, but the book is generally identified as the series' longest by word count and standard English page counts.

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. Dolores Umbridge becomes a major antagonist during the school year.

Length comparisons can be misleading if readers compare different editions or translations. The next-longest English books are commonly Harry Potter and the Goblet of Fire and Harry Potter and the Deathly Hallows, but neither exceeds Order of the Phoenix in the original English series.