Horace Porter (April 15, 1837 – May 29, 1921) was an American soldier and diplomat who served as a lieutenant colonel, ordnance officer and staff officer in the Union Army during the American Civil War, personal secretary to General and PresidentUlysses S. Grant and to General William Sherman, vice president of the Pullman Palace Car Company and U.S. Ambassador to France from 1897 to 1905. In 1866, he was appointed to the brevet grade of brigadier general, United States Army.
Lieutenant Colonel Horace Porter accompanied General Grant to Louisville in 1865 to oversee the plebiscite on Kentucky's secession. While at dinner with their Confederate counterparts Robert E. Lee and Charles Marshall, Porter remarked that fears of smuggling rifles across state lines were futile, as there were already plenty of rifles in the state. The next day, Porter was one of those who rushed to the scene of an attempt on Lee's life.