William Bross Lloyd (February 24, 1875 – June 30, 1946) was an American attorney and political activist.
The oldest son of the muckraking journalist Henry Demarest Lloyd and Jessie Bross, daughter of Chicago Tribune founder William Bross, William Bross Lloyd is best remembered as a founding member and financial angel of the fledgling Communist Labor Party of America, forerunner of the Communist Party USA.