If you searched for the names of the two atomic bombs, you are asking about one of the most significant facts of twentieth-century history: the two nuclear weapons used in warfare in August 1945, during the final weeks of the Second World War. The names of the two atomic bombs were Little Boy and Fat Man. Little Boy was used over the Japanese city of Hiroshima on 6 August 1945, and Fat Man was used over the Japanese city of Nagasaki on 9 August 1945. This guide explains those names, what the names referred to, why the weapons were given those names, and the historical context in which they were used, in neutral, factual terms and without graphic detail.
The names of the two atomic bombs are often the first thing students, readers and researchers want to pin down, because the two weapons are so frequently mentioned together in history books, documentaries and classroom discussions. It is easy to mix up the names of the two atomic bombs, since both weapons were dropped within three days of each other and both are associated with the end of the war. Keeping them straight is simple once you link each name to its city and date: Little Boy with Hiroshima on 6 August, and Fat Man with Nagasaki on 9 August. The rest of this article explains how those names arose and why the events matter so much in the historical record.
names of the two atomic bombs: The Short Answer
The short answer is the one given above, and it is worth stating plainly again for clarity. The names of the two atomic bombs dropped in Japan in 1945 were Little Boy, used at Hiroshima, and Fat Man, used at Nagasaki. Both were nuclear weapons developed during the Second World War, and both remain the only nuclear weapons ever used in warfare. That last fact is central to their historical importance: the events of August 1945 are not only about the end of one war, but also about the beginning of the nuclear age, in which the existence of such weapons has shaped international politics ever since.
The two weapons behind the names of the two atomic bombs were different designs, and their names reflected their shapes. Little Boy was a long, slim weapon, while Fat Man was a rounder, wider weapon. Those physical descriptions became their informal names during development, and the names stuck in the historical record. They were not official poetic titles chosen for public effect; they were working names used by the people building the weapons, and they entered history because the weapons themselves became so historically significant. Understanding the names of the two atomic bombs in this way, as practical labels that became permanent, helps explain why they sound so plain compared with the scale of the events they are attached to.
Little Boy and Hiroshima, 6 August 1945
Little Boy was the weapon used over Hiroshima on the morning of 6 August 1945. Its name came from its shape: it was relatively long and narrow compared with the other weapon, and those working on it referred to it by the descriptive name Little Boy. It was a gun-type design, a term that refers to the internal method by which the weapon was constructed, and it used uranium as its nuclear material. The weapon was delivered by a United States bomber aircraft, and it exploded above the city rather than on impact with the ground.
Hiroshima was a significant Japanese city and a military centre, which is why it had been selected as a target. The bombing of Hiroshima was the first use of a nuclear weapon in warfare, and it immediately became a world-changing event. News of a weapon of entirely new power spread quickly, and governments around the world began to grasp that warfare had entered a new era. In the historical record, Hiroshima and Little Boy are inseparable: when people refer to the first atomic bombing, they are referring to this event, on this date, in this city, with this weapon.
Fat Man and Nagasaki, 9 August 1945
Fat Man was the weapon used over Nagasaki on 9 August 1945, three days after Hiroshima. Its name likewise came from its shape: it was a rounder, bulkier weapon than Little Boy, and the descriptive name Fat Man was used for it during development. It was a different design from Little Boy, using plutonium as its nuclear material and a different internal method. The two weapons were therefore not simply two copies of the same device; they were two distinct designs, developed in parallel as part of the same wartime programme.
Nagasaki was a port city in southern Japan, and like Hiroshima it had military and industrial significance. The bombing of Nagasaki was the second and, to date, last use of a nuclear weapon in warfare. Together, the two bombings form a single chapter in history, but they are distinct events with distinct dates, cities and weapons, and keeping the names of the two atomic bombs attached to the correct city is the key to describing them accurately. Fat Man belongs with Nagasaki and 9 August, just as Little Boy belongs with Hiroshima and 6 August.
The Wartime Programme Behind the Weapons
Both weapons were products of the Manhattan Project, the large United States wartime research and development programme that brought together scientists, engineers, military planners and industrial facilities to develop nuclear weapons before the war ended. The programme was one of the largest scientific efforts of its time, involving research sites and production facilities across the United States. Its existence was kept secret during the war, and the scale of the effort only became widely known after the weapons were used.
The Manhattan Project was driven by the context of the Second World War, a global conflict that had already lasted for years and that involved intense competition in science and weaponry. The decision to use the weapons, taken by United States political and military leadership in the summer of 1945, remains one of the most debated decisions in modern history. Historians continue to discuss the reasoning behind it, the alternatives that were considered, and the consequences that followed. This guide does not take a position in that debate; it records the facts behind the names of the two atomic bombs that are not in dispute: the cities, the dates, and the sequence of events that followed.
names of the two atomic bombs: What Happened Next
In the days after the two bombings, Japan’s leadership moved towards surrender. On 15 August 1945, Japan announced its surrender, and the formal surrender ceremony took place on 2 September 1945, bringing the Second World War to an end. The names of the two atomic bombs are therefore closely linked in the historical timeline to the end of the war, and they are often taught as part of that final chapter. The speed of the ending, coming so soon after years of war across Asia and the Pacific, is one reason the events remain so prominent in history education.
The longer aftermath shaped the decades that followed. The cities of Hiroshima and Nagasaki were rebuilt, and both cities later became centres for peace education and for remembering the events of August 1945. Memorials, museums and annual commemorations in both cities keep the history visible, and survivors’ testimonies have been recorded as part of the historical record. On the international stage, the existence of nuclear weapons led to new treaties, new alliances and new debates about deterrence, disarmament and the rules of war. The names of the two atomic bombs thus sit at the start of a much longer story about how the world has lived with nuclear weapons ever since.
The Two Bombs at a Glance
| Weapon name | City | Date | What the name described |
|---|---|---|---|
| Little Boy | Hiroshima | 6 August 1945 | A long, slim weapon shape |
| Fat Man | Nagasaki | 9 August 1945 | A round, wide weapon shape |
This table is the simplest way to remember the facts. If you only take one thing from this guide, it should be the pairing: Little Boy with Hiroshima on 6 August, and Fat Man with Nagasaki on 9 August. Those pairings appear in textbooks, museum displays and reference works around the world, and they are the standard way the events are identified.
Frequently Asked Questions
What were the names of the two atomic bombs?
The names of the two atomic bombs were Little Boy and Fat Man. Little Boy was used at Hiroshima and Fat Man was used at Nagasaki.
Which bomb was dropped on Hiroshima?
Little Boy was the bomb used over Hiroshima, on 6 August 1945.
Which bomb was dropped on Nagasaki?
Fat Man was the bomb used over Nagasaki, on 9 August 1945.
Why were they called Little Boy and Fat Man?
The names described the weapons’ shapes during development. Little Boy was long and slim, while Fat Man was round and wide, and those working names became the names recorded in history.
Have nuclear weapons been used in warfare since 1945?
No. The bombings of Hiroshima and Nagasaki remain the only uses of nuclear weapons in warfare, which is a major reason they continue to be studied and commemorated.
Conclusion
The names of the two atomic bombs are Little Boy, used at Hiroshima on 6 August 1945, and Fat Man, used at Nagasaki on 9 August 1945. Their plain, descriptive names came from their shapes, and they have remained attached to those two cities and dates ever since. The events belong to the final weeks of the Second World War and to the beginning of the nuclear age, and they continue to be remembered through education, memorials and public discussion. Remembering the names correctly matters, because it keeps the historical record clear: two distinct weapons, two distinct cities, three days apart, at the end of a world war. For more history and reference guides on this site, see our look at the history of the Nguyen name and our roundup of the Academy Award Best Picture nominees for 2008.
