John Knowles Herr (October 1, 1878 – March 12, 1955) was a career American soldier. Herr served for 40 years in the United States Cavalry and participated in the final battles of World War I as chief of staff of the 30th Division, but is best remembered for being the last Chief of U.S. Cavalry. In March 1938 Major General Herr was appointed Chief of Cavalry and became a fierce advocate of traditional horse cavalry troops. He defended cavalry as an independent branch of service and opposed conversion of mounted troops into mechanized or armored units. Herr's affection to horse, "somewhat quixotic" for the period, temporarily made him "a hero and a standard bearer" to generations of officers indoctrinated in cavalry tactics.