What is the most sold Harry Potter book?

The most sold Harry Potter book is "Harry Potter and the Philosopher's Stone", also known as "Harry Potter and the Sorcerer's Stone" in the US. It is the first book in the Harry Potter series written by J.K. Rowling. The book was published in 1997 and has since sold over 120 million copies worldwide, making it one of the best-selling books of all time.