Koishikawa Kōrakuen Garden (小石川後楽園) is in Koishikawa, Bunkyō, Tokyo, adjacent to Tokyo Dome City. It is one of two surviving Edo period clan gardens in modern Tokyo, the other being Kyu Shiba Rikyu Garden, and one of the oldest and best preserved parks in Tokyo.

Mitsukuni named this garden "Kōraku-en" (Kōraku means "enjoying afterwards") after a Chinese teaching of "a governor should worry before people and enjoy after people". The garden shows strong Chinese character in its design, as it was influenced by the West Lake of Hangzhou.

Kōrakuen was appointed as a special place of scenic beauty and a special historic site based on the cultural properties protection law of Japan.