Sydney Hobart Ball (December 11, 1877 – April 3, 1949) was an American geologist and mining engineer. Educated at the University of Wisconsin, Ball spent his early career in public service. In 1907 he left the US to prospect for minerals in the Belgian Congo for the Forminière company. Ball discovered the first part of the Congo-Angola diamond field, which proved a valuable source of revenue. Returning to America, Ball established a private practice and acted as consultant to a number of public bodies.