Which Harry Potter novel was published in the United Kingdom on 21 June 2003?

Harry Potter and the Order of the Phoenix was published in the United Kingdom on 21 June 2003.

It is the fifth novel in J.K. Rowling’s seven-book series. The story follows Harry’s fifth year at Hogwarts, during which the Ministry of Magic attempts to control the school and deny that Voldemort has returned. Harry and his friends respond by forming Dumbledore’s Army to practise defensive magic.

The book is the longest in the original series by word count. Its plot expands the political conflict, introduces the oppressive Hogwarts teacher Dolores Umbridge, and develops Harry’s connection with Voldemort through the Department of Mysteries.

The novel’s release was a major publishing event, with midnight sales and large crowds in several countries. It was later adapted as the fifth film, released in 2007, starring Daniel Radcliffe as Harry Potter.