| Jun'ya Koizumi | |
| Native Name Lang: | ja |
| Office1: | Member of the Imperial Diet of Japan (House of Representatives) |
| Term Start1: | 1937 |
| Term End1: | 1947 |
| Office2: | Member of the House of Representatives |
| Term Start2: | 1952 |
| Term End2: | 1969? |
| Office3: | Director-General of the Japan Defense Agency |
| Primeminister3: | Hayato Ikeda and Eisaku Satō |
| Term Start3: | 18 July 1964 |
| Term End3: | 3 June 1965 |
| Predecessor3: | Fukuda Tokuyasu |
| Successor3: | Raizo Matsuno |
| Birth Date: | 24 January 1904 |
| Birth Place: | Higashi-Kaseda, Kagoshima Prefecture, Empire of Japan |
| Party: | LDP (after 1952) |
| Alma Mater: | Nihon University |
| Spouse: | Yoshie Koizumi |
| Children: | 6, including Junichiro |
| Birth Name: | Junya Samejima |
| Relatives: | Koizumi Matajirō (father-in-law) |
Junya Koizumi (小泉 純也, Koizumi Jun'ya) (January 24, 1904 – August 10, 1969) was a Japanese politician who served as Director General of the Japan Defense Agency during the 1960s.
Koizumi was born in Higashi-Kaseda, Kagoshima Prefecture (now part of Minami-Satsuma); his family were fishermen. He attended high school at night while working in a department store, and then attended law classes at Nihon University while working as a secretary to a Diet member. He graduated in 1930 and joined the Rikken Minseitō political party. He was elected to the Diet in 1937.
He married Yoshie Koizumi, the daughter of Rikken Minseitō director and postal minister Matajirō Koizumi, taking her family name. Junya and Yoshie Koizumi had six children, including Jun'ichirō Koizumi, who later became the Prime Minister of Japan.[1]
Koizumi was purged from politics by the Allied occupation government in the late 1940s, but returned to the Diet in 1952. He was a close ally of Nobusuke Kishi in the postwar years, served as Vice-Minister of Justice under Ichirō Hatoyama and became Director General of the Japan Defense Agency under Hayato Ikeda and Eisaku Satō.