The 1331 siege of Akasaka was a battle of the Genkō War, taking place during the final years of Japan's Kamakura period, at Shimo Akasaka-jō (下赤坂城, "lower Akasaka fortress") near modern-day Osaka.
Shimo Akasaka, a mountain fortress, was built that year, and held by Kusunoki Masashige, a general of Emperor Go-Daigo's armies. On several occasions throughout the year, forces of the Hōjō regents attempted to take the fortress. With great ingenuity, Masashige defended the fort. However, after the Hōjō cut the water supply to the fortress, it fell.
Kusunoki then built a second "Akasaka" fortress, a short distance away, dubbing it Kami Akasaka-jō (上赤坂城, "upper Akasaka fortress"). This too was besieged, and fell, in 1333.