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