Little Boy was the code name of the atomic bomb dropped on Hiroshima on August 6, 1945.
The uranium-235 weapon was released from the B-29 bomber Enola Gay and detonated over Hiroshima at approximately 8:15 a.m. local time. It was the first nuclear weapon used in warfare.
A second atomic bomb, Fat Man, was dropped on Nagasaki three days later. The two weapons used different designs: Little Boy used a gun-type mechanism, while Fat Man used an implosion design.
The Hiroshima bombing formed part of the final crisis preceding Japan’s surrender. It is important not to confuse Little Boy with Trinity, the code name for the first nuclear weapons test, conducted in New Mexico in July 1945.