Koizumi (小泉 "small fountain", 古泉 "old fountain") is a Japanese family name.
It may describe one of several Koizumi railway stations.
It can refer to a number of people, including the following members of the prominent Koizumi family:
Junichiro 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
Koizumi Matajirō (小泉 又次郎, 1865–1951), Japanese politician and the father-in-law of Junya Koizumi
Kotaro 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
