Ceremonies get under way with a moment of silence at 7:55 am, the exact time the bombing began in 1941.
2,390 service members and 49 civilians killed in the attack which led to a conflict that cost the United States 418,500 lives. The war in the Pacific only ended when the Americans unleashed the power of the atom.
The crew of a Navy guided-missile destroyer will stand on deck while the ship passes the USS Arizona, a battleship that still lies in the harbour where it sank decades ago. Hawaii Air National Guard aircraft will fly overhead in missing man formation.
The Navy and National Park Service are hosting the ceremonies, which are being held in remembrance of the 2,390 service members and 49 civilians killed in the attack.
American airmen dropped Little Boy on the city of Hiroshima on 6 August 1945, followed by Fat Man over Nagasaki on 9 August. Close to 250,000 people died as a result of the use of the Atomic weapons.
As any Axis and Allies fan knows the Japanese strategy was flawed from the get go. It was just a matter of time before the Americans rebuild. The vast economic power of the USA ensured a victory.