* Penguin Random House: This is actually the largest publisher in the world, formed by the merger of Penguin and Random House.
* HarperCollins: Another major player, owned by News Corp.
* Simon & Schuster: Owned by Paramount Global, known for its diverse range of books.
* Macmillan: A large publisher with a variety of imprints, including Tor and St. Martin's Press.
* Hachette Book Group: A subsidiary of the French media group Lagardère, known for its strong children's book division.
It's important to note that the "largest" publisher can change depending on how you measure size (e.g., revenue, number of books published, market share).