Which atomic bomb was dropped on Hiroshima on 6 August 1945?

The atomic bomb dropped on Hiroshima on 6 August 1945 was Little Boy.

Little Boy was a uranium-235 gun-type fission weapon developed by the Manhattan Project. The B-29 Enola Gay released it over Hiroshima at about 8:15 a.m. local time. The bomb detonated roughly 600 metres above the city, producing enormous blast, heat, and radiation.

Little Boy was the first nuclear weapon used in warfare. Its target was Hiroshima, an important military and logistical centre. Three days later, the United States dropped Fat Man, a plutonium implosion weapon, on Nagasaki.

A common mix-up is reversing the two bomb names. Little Boy was used against Hiroshima, while Fat Man was used against Nagasaki. The bombings, combined with the Soviet entry into the war against Japan, preceded Japan’s announcement that it would accept the Allied surrender terms.