John Sherman Cooper (August 23, 1901 – February 21, 1991) was a politician, jurist, and diplomat from the U.S. state of Kentucky. He served three non-consecutive, partial terms in the United States Senate before being elected to two full terms in 1960 and 1966. He also served as U.S. Ambassador to India from 1955 to 1956 and U.S. Ambassador to East Germany from 1974 to 1976. He was the first Republican to be popularly elected to more than one term as a senator from Kentucky and, in both 1960 and 1966, he set records for the largest victory margin for a Kentucky senatorial candidate from either party.