For the first time, a representative of the United States, which dropped the bomb on the city, is attending.
About 140,000 people were killed or died within months of the bomb being dropped by a US aircraft in 1945 in the final days of World War II.
Japan surrendered after a second atomic bomb was dropped on Nagasaki three days later on 9 August.
The site where the bomb was dropped 65 years ago was filled with the sound of choirs of school children and the solemn ringing of bells.
A minute's silence was held at 0815 - the exact time the bomb fell.
Offerings of water were made to the 140,000 who died, as many died of thirst in the days and weeks after the attack.
UN Secretary General Ban Ki-moon, who was also attending the ceremony for the first time, presented flowers at the Eternal Flame in Hiroshima's Peace Memorial Park.
"Life is short, but memory is long," he said.
"For many of you, that day endures... as vivid as the white light that seared the sky, as dark as the black rains that followed."
He told the gathered crowd of 55,000 people from 74 nations that the time had come to move from "Ground Zero, to Global Zero" - a world without any nuclear weapons.
Japan, the only country to have been attacked with nuclear weapons, has been pushing for their abolition.
Top objective
Hiroshima's mayor welcomed Washington's decision to send US Ambassador John Roos, saying he hoped the event would boost global denuclearisation.
Mr Roos said the memorial was a chance to show resolve towards nuclear disarmament, which US President Barack Obama has said is a top objective.
"For the sake of future generations, we must continue to work together to realise a world without nuclear weapons," Mr Roos said in a statement.
The presence of Mr Roos is being seen by some in Japan as a sign that President Obama may visit Hiroshima when he comes to Japan.
If so, he would be the first sitting US president to visit the city.
Some Japanese have called on the US to apologise for the atomic bombings, but the BBC's Roland Buerk, in Hiroshima, says this is unlikely to happen.
10 Comments
Lyle Hutchins 1
Bull SHIT!!! That COON PUSSY, Obama, will sell out to the Japs also. Who started the shit in the Pacific??? Who ended it in Nagasaki???
Who owes who an Apology???
The Son, of a Former Marine (who fought the Japs)
Lyle
Anonymous
I dont think we should apologize. However I posted this as is where I found it on BBC's Website. With the added pic from Wikipedia. But we cannot forget the horrors that nukes have on every soul on the planet. I hope we never have to use nukes in war again or at least I hope I am dead if it comes to that.
Lyle Hutchins 1
Yes, I hope we don't use nukes again. But we (US) need to keep them!! Look what the Ragheads are doing, and that fat slant/eyed asshole with thick glasses, commy, Chineese. Don't think for a moment that we (US) can afford to abandion our NUKES.
Obama is the person to abandin them and leave our skys and boarders wide open!!!
Don't want to use them eather. I look at it like hav'n a gun. Its best to have a gun, and not use it, than needing one and not hav'n it!! Cause the other guy knows you got one, or several.
If our Government had some Balls, (Bush,and Obama, Congress) they would have given the Chi-Coms. and the Ragheads a headsup, Eather dismantle your Nucular Programs, or the US will Help you!! United States suggests you do this on your own.
In 60 days we will observe your progress of the dismantling. If you choose not to comply with the demands, our Airforce will assist you in your labors!! STAND CLEAR MO-FO!!!!
But as we all know, Barry will bow down, apoligize, with his tail between his legs.
Lyle
I'm Pissed,
go'n 2 bed
LLE
The Japanese attacked us and gave no quarter. The "sleeping giant" [Yamamoto quote] woke up, and counterattacked, giving no quarter. Apologize for WHAT!? An apology would be the ultimate absurdity and it would represent another advertisement of what an abysmal, irrational--yes, even insane lesson the Obama administration has for any would-be enemy of the USA. it would say, in effect, that the more morally high-ground decision [then], was to invade the Japanese mainland and suffer perhaps a million more allied casualties/deaths. I am fairly certain that such a philosophy would meet the definitions of both "insanity" and psychosis.
ivantank
apologist for the Bataan death march and for the brutal murder and rape of Philippines..then we can talk
catfish88
Good point ivantank!
HKBauer
Apologize sure we will apologize after they apologize for china, the phillipines, marshall islands, Wake, Iwo Jima, oh and PEARL F*CKING HARBOR! How about the apology to my grandads, my great uncles, and all the rest of those who fought and died fighting the then we will apologize or maybe not!! I for one am glad we nuked the bastards!
greg az
Japanese atrocities in and before world war II were unbelievable.. When we landed in the Philippines we opened up some barracks in Cavite that had last been used in WWII (Cavite is across the bay from manila, Sangley pt. Naval Air Station) This was like 22 years after the war and thier were still horrible feelings about the Japanese in the Philippines..
If you want to read some sick stuff check out the "rape of Nanking" this was when the Japanese took over Nanking China.. Some of the Japanese atrocities during this siege are beyond the ability to comprehend.. and my desire to put on paper..
I'm not naive to what happens in war.. Some times its a defence mechanism, but what happened in China goes beyond anything ive ever read about..
rommelvspatton
The horrible feelings held for the Japanese is held all over the pacific rim and asia.
Not since the Mongols had someone slaughtered and held so many different peoples in such discontent.
Thats SAYING ALOT, I mean theres been some nasty bloodshed in the last 1000 years.
rommelvspatton
Never been another one dropped.
Its the ultimate deterrence, mutual destruction. You will never see 2 powers with nuclear weapons go to war.
On the other hand, We would of already destroyed N Korea if they didnt have their nukes.