The Harmsworth Cup, popularly known as the Harmsworth Trophy, is a historically important British international trophy for motorboats.

Alfred Charles William Harmsworth, 1st Viscount Northcliffe, was a British newspaper and publishing magnate. As owner of the Daily Mail and the Daily Mirror, he was an early developer of popular journalism, and he exercised vast influence over British popular opinion during the Edwardian era. Lord Beaverbrook said he was "the greatest figure who ever strode down Fleet Street." About the beginning of the 20th century there were increasing attempts to develop popular journalism intended for the working class and tending to emphasize sensational topics. Harmsworth was the main innovator. He said, "News is something someone wants to suppress. Everything else is advertising."