John Watson Foster was an American diplomat and military officer, as well as a lawyer and journalist. His highest public office was U.S. Secretary of State under Benjamin Harrison, although he also proved influential as a lawyer in technically private practice in the international relations sphere.

Foster moved to Washington, D.C. under Republican President Ulysses S. Grant, as well as had a summer home in Watertown, New York. As a reward for his political service after the Republican Party split in 1872 as a result of scandals and rampant corruption in Grant’s first administration, successive Republican Presidents Grant, Rutherford B. Hayes and James A. Garfield appointed Foster the U.S. Ambassador to Mexico (1873–1880), then to Russia (1880–1881). President Chester A. Arthur made Foster the United States Ambassador to Spain (1883–1885).

In Benjamin Harrison’s administration, Foster served as a State Department “trouble shooter” before becoming Secretary of State for the final six months of Harrison’s term (from June 29, 1892, to February 23, 1893). As such, Foster replaced James Gillespie Blaine, who had succumbed to Bright’s disease, of which he later died. As Secretary of State, Foster helped direct the overthrow of the Hawaiian monarchy.

After leaving public office, Foster remained in Washington and invented a new type of legal practice, lobbying for large “corporations seeking favors in Washington and chances to expand abroad.” Foster also used his government and political contacts to secure legal fees as counsel to several foreign legations. He also continued to serve Presidents part-time on diplomatic missions. As such, Foster negotiated trade agreements with eight countries, brokered a treaty with Britain and Russia concerning seal hunting in the Bering Sea, and negotiated the Treaty of Shimonoseki of 1895, technically as legal consultant and commissioner for the Qing Dynasty in which China recognized Korean independence as well as ceded Taiwan to the victorious Japanese after the First Sino-Japanese War.