Kenji Kimihara (君原 健二, Kimihara Kenji, born March 20, 1941) is a retired Japanese long-distance runner. He competed in the marathon at the 1964, 1968 and 1972 Olympics and finished in eighth, second and fifth place, respectively. He won two gold medals in the marathon at the Asian Games in 1966 and 1970, and won the Boston Marathon in 1966. He was very successful on the Japanese road racing circuit, winning the Tokyo International Marathon and Lake Biwa Marathon in both 1963 and 1964, and registering four wins at the Beppu-Ōita Marathon between 1967 and 1973.