Mount Akagi (赤城山, Akagi-yama, Red Castle) is a stratovolcano in Gunma Prefecture, Japan.

An older stratovolcano was partially destroyed by edifice collapse, producing a debris-avalanche deposit along the south flank.

Construction of the central cone in the late-Pleistocene summit caldera began following the last of the plinian eruptions about 31,000 years ago.

During historical time unusual activity was recorded on several occasions during the 9th century, but reported eruptions in 1251 and 1938 are considered uncertain.

To the top of Mount Kurobi, the highest point of this mountain, it takes about three hours from the Akagi Hiroba Bus Stop.