The Kantō Plain , in the Kantō region of central Honshu, is the largest plain in Japan. Its 17,000 km2 covers more than half of the region extending over Tokyo, Saitama Prefecture, Kanagawa Prefecture, Chiba Prefecture, Gunma Prefecture, Tochigi Prefecture, and Ibaraki Prefecture.

The Kantō region is a geographical region of Honshu, the largest island of Japan. In a common definition, the region includes the Greater Tokyo Area and encompasses seven prefectures: Gunma, Tochigi, Ibaraki, Saitama, Tokyo, Chiba, and Kanagawa. Slightly more than 45 percent of the land area within its boundaries is the Kantō Plain. The rest consists of the hills and mountains that form land borders with other regions of Japan.