Koishikawa (小石川 little stoney river) is a district of Bunkyo, Tokyo. It consists of five sub-areas, 1-5 chome (1~5丁目). It is located nearby with the same name are two well regarded gardens: the Koishikawa Botanical Garden (related to the University of Tokyo) in Hakusan, and the Koishikawa Korakuen Garden in Korakuen.
The Koishikawa arsenal was an important military installation during the Meiji era.
Bunkyo operates the local public elementary and middle schools.