Koizumi (小泉 "small fountain", 古泉 "old fountain") is a Japanese family name.

It may describe one of two Koizumi Stations.

It can refer to a number of people, including the following members of the prominent Koizumi family:

  • Junichirō Koizumi (小泉 純一郎, born 1942), former prime minister of Japan
  • Junya Koizumi (小泉 純也, 1904–1969), a second-generation Diet member and the father of Junichiro Koizumi
  • Matajirō Koizumi (小泉 又次郎, 1865–1951), Japanese politician and the father-in-law of Junya Koizumi
  • Kōtarō Koizumi (小泉 孝太郎, born 1978), an aspiring actor and the first son of Junichiro Koizumi
  • Shinjirō Koizumi (小泉 進次郎, born 1981), a fourth-generation Diet member and the second son of Junichiro Koizumi

Other individuals

Fictional characters

  • Gen-ichi Koidzumi (小泉 源一, 1883-1953), botanist whose standard abbreviation in botanical works is Koidz.