Horace Greeley Knowles (October 20, 1863 – November 2, 1937) was an American attorney and diplomat, who served as an ambassador under three U.S. presidents between 1907 and 1913.

[2] For a period, Knowles remained active in Republican politics: during the 1928 presidential election he campaigned actively for Herbert Hoover, warning that if Democratic nominee Al Smith were victorious, the nation would experience high unemployment and widespread depression.

[3] After leaving the foreign service, Knowles returned to practicing law, and appeared often before the United States Court of Claims.

[citation needed] In the 1920s, Knowles became "a consistent critic of the policy of the United States in Central America, the Dominican Republic, and Haiti".

[4] He was also a critic of the Second Italo-Abyssinian War, and became treasurer of the "Committee for Ethiopia", conducting a fundraising drive that collected over $1 million for medical aid to the Ethiopians.