Which Harry Potter book became the first novel to sell more than 10 million copies in a single day?

Harry Potter and the Deathly Hallows became the first novel to sell more than 10 million copies in a single day.

The seventh and final Harry Potter book was released worldwide on 21 July 2007. In the United States, Scholastic reported first-day sales of more than 8 million copies, while worldwide sales exceeded 11 million copies in its first 24 hours. The launch demonstrated the extraordinary scale of the series’ readership.

The novel concludes Harry’s conflict with Lord Voldemort and answers long-running questions about the Deathly Hallows, Horcruxes and Severus Snape. Its enormous pre-release demand was driven by the book’s status as the finale and by years of speculation about which characters would survive.

The record is easy to confuse with the first-day performance of earlier books, especially Harry Potter and the Half-Blood Prince. Deathly Hallows was the final novel and produced the largest launch in the series.