Bloomsbury first published J.K. Rowling’s Harry Potter books in the United Kingdom.
Bloomsbury released Harry Potter and the Philosopher’s Stone on 26 June 1997. The company then published the remaining six novels in the main series, concluding with Harry Potter and the Deathly Hallows in 2007.
Barry Cunningham, then an editor at Bloomsbury, acquired the manuscript after Rowling submitted it through literary agent Christopher Little. The first book’s success rapidly transformed Rowling’s career and made the series a central part of Bloomsbury’s publishing identity.
The U.S. editions were published by Scholastic under the title Harry Potter and the Sorcerer’s Stone for the first book. This is why Bloomsbury is the most specific answer for the original British publisher, while Scholastic is associated with the American editions.