John Allen Hemphill (December 19, 1927 - May 21, 2021) was a major general in the United States Army. He served as Director of Operations (J-3) of the United States Readiness Command. He was a 1951 graduate of the United States Military Academy with a B.S. degree in military science. Hemphill graduated from the Infantry School Advanced Course in 1957, the Air Command and Staff College in 1961 and the Armed Forces Staff College in 1965. He later also graduated from the United States Army War College. After his death, Hemphill was interred at the West Point Cemetery on August 23, 2021.