Honshu is the largest of Japan's over 3,000 island; it is approximately 1,600 km long and 250 km at its widest. The total area of 230,000 km² makes it bigger than the island of Great Britain and roughly the same size as the state of Minnesota.

Mountainous and volcanic, Honshu has frequent earthquakes. Japan's highest peak, the active volcano Mount Fuji and its longest river, the Shinano River are to be found on Honshu.

The island is divided into 5 regions: Tohoku, Kanto, Chubu, Kansai and Chugoku; containing the 34 prefectures of; Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima, Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Kanagawa, Niigata, Toyama, Ishikawa, Fukui, Yamanashi, Nagano, Gifu, Shizuoka, Aichi, Mie, Shiga, Kyoto, Osaka, Hyogo, Nara, Wakayama, Tottori, Shimane, Okayama, Hiroshima and Yamaguchi.

The population of roughly 100 million is mostly concentrated in urban centers focused on the cities of Tokyo, Nagoya and Osaka. With 25% of the nation's population residing in the Greater Tokyo Area, a vast conurbation which encompasses the cities of Tokyo, Kawasaki, Yokohama, Saitama and Chiba.

The belt which stretches from Tokyo as far as Hiroshima in the west, along the southern coast of Honshu is home to the bulk of Japan's industrial production.