Hiroshima was founded in 1589 as a castle town on the Ōta River delta. Following the Meiji Restoration in 1868, Hiroshima rapidly transformed into a major urban center and industrial hub. In 1889, Hiroshima officially gained city status. The city was a center of military activities during the imperial era, playing significant roles such as in the First Sino-Japanese War, the Russo-Japanese War, and the two world wars.

Hiroshima was the first military target of a nuclear weapon in human history. This occurred on August 6, 1945 in the Pacific theatre of World War II, at 8:15 a.m., when the United States Army Air Forces (USAAF) dropped the atomic bomb "Little Boy" on the city. Most of Hiroshima was destroyed, and by the end of the year between 90,000 and 166,000 had died as a result of the blast and its effects. The Hiroshima Peace Memorial (a UNESCO World Heritage Site) serves as a memorial of the bombing.

Since being rebuilt after the war, Hiroshima has become the largest city in the Chūgoku region of western Honshu.

During World War II, the Second General Army and Chūgoku Regional Army was headquartered in Hiroshima, and the Army Marine Headquarters was located at Ujina port. The city also had large depots of military supplies, and was a key center for shipping.

The bombing of Tokyo and other cities in Japan during World War II caused widespread destruction and hundreds of thousands of civilian deaths. There were no such air raids on Hiroshima. However, a real threat existed and was recognized. To protect against potential firebombings in Hiroshima, school children aged 11–14 years were mobilized to demolish houses and create firebreaks.

On Monday, August 6, 1945, at 8:15 a.m. (Hiroshima time), the nuclear weapon "Little Boy" was dropped on Hiroshima from an American Boeing B-29 Superfortress, the Enola Gay, flown by Paul Tibbets (23 February 1915 – 1 November 2007), directly killing at least 70,000 people, including thousands of Korean slave laborers. Fewer than 10% of the casualties were military. By the end of the year, injury and radiation brought the total number of deaths to 90,000–140,000. The population before the bombing was around 345,000. About 70% of the city's buildings were destroyed, and another 7% severely damaged.

The public release of film footage of the city following the attack, and some of the Atomic Bomb Casualty Commission research on the human effects of the attack, were restricted during the occupation of Japan, and much of this information was censored until the signing of the Treaty of San Francisco in 1951, restoring control to the Japanese.

Hiroshima was proclaimed a City of Peace by the Japanese parliament in 1949, at the initiative of its mayor, Shinzo Hamai (1905–1968). As a result, the city of Hiroshima received more international attention as a desirable location for holding international conferences on peace as well as social issues. As part of that effort, the Hiroshima Interpreters' and Guide's Association (HIGA) was established in 1992 to facilitate interpretation for conferences, and the Hiroshima Peace Institute was established in 1998 within the Hiroshima University. The city government continues to advocate the abolition of all nuclear weapons and the Mayor of Hiroshima is the president of Mayors for Peace, an international Mayoral organization mobilizing cities and citizens worldwide to abolish and eliminate nuclear weapons by 2020.

On May 27, 2016, Barack Obama became the first sitting United States president to visit Hiroshima since the atomic bombing.

Hiroshima is situated on the Ōta River delta, on Hiroshima Bay, facing the Seto Inland Sea on its south side. The river's six channels divide Hiroshima into several islets. Thankyou 😊.