Which J.K. Rowling novel is the longest in the original Harry Potter series by word count?

J.K. Rowling’s longest Harry Potter novel by word count is Harry Potter and the Order of the Phoenix.

The fifth book contains roughly 257,000 words in its English edition, making it the longest novel in the seven-book series. Its length reflects a broad plot involving Hogwarts under Ministry interference, Harry’s anger and isolation, and the re-formation of the Order of the Phoenix.

Readers sometimes assume Harry Potter and the Goblet of Fire is the longest because it is physically substantial and introduces several major storylines. The final book, Harry Potter and the Deathly Hallows, is also long, but its word count is lower than Order of the Phoenix.

Page counts can vary between editions because of paper size, typography and regional formatting. Word count is therefore the clearest basis for comparing the original English novels.