Which Harry Potter novel is the longest in the UK edition by word count?

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

Published in 2003, the fifth book contains roughly 257,000 words in the British edition, making it the largest of the seven main novels by word count. Its length reflects a storyline involving the Ministry of Magic, the return of Lord Voldemort, Harry’s visions and the formation of Dumbledore’s Army.

Page totals can vary between editions because of typesetting, trim size and language. That is why word count is a more useful comparison than simply counting pages. The Order of the Phoenix is often remembered as the longest book, although the final novel is also substantial.

The book was adapted into a 2007 film starring Daniel Radcliffe as Harry. The film necessarily omits or compresses many subplots from the long novel.