A unit of explosive power roughly equal to 15 kilotons, or about 6.28 x 1013 joules. Equal to the yield of Little Boy, the atomic bomb dropped on Hiroshima, and is named to signify this. Often written as "hiroshima bomb". Ex: "Even the smallest new warheads each pack over 300 hiroshima bombs worth of explosive force."

Not an official unit of measurement, the term is not used in scientific work, but more commonly in popular literature or work intended for public consumption. Few civilians have much of sense of what a megaton is, or even a kiloton for that matter. As such, the detonation of Little Boy, the world's most well-known high-yield explosion, often serves as a useful reference point when discussing nuclear weapons.

May also refer to other aspects of the bombing of Hiroshima, such as amount of fallout or deaths caused.