Which Harry Potter novel was the first in the series to be published on 21 July?

Harry Potter and the Deathly Hallows was the first Harry Potter novel in the series to be published on 21 July.

The seventh and final novel was released worldwide on 21 July 2007. It concludes Harry’s struggle against Lord Voldemort and follows the trio of Harry, Ron Weasley, and Hermione Granger as they search for Horcruxes rather than returning normally to Hogwarts.

The book sold exceptionally quickly. In the United States, Scholastic reported that more than eight million copies were sold during its first 24 hours. Its publication date was widely publicized as the conclusion to the main novel sequence, although later works expanded the Wizarding World in other formats.

Earlier novels used other launch dates. Harry Potter and the Half-Blood Prince appeared in July 2005, but it was not released on 21 July. The date is therefore a precise publication clue for the final book.