Usain Bolt has cemented his place as a sporting legend as he scorched to the second-fastest 100 metres ever, in a superb 9.63 seconds.
The Jamaican's 9.58-second run to take the 2009 world title is the only quicker time in the history of the event.
Sunday's brilliant display silenced the doubters who predicted his hamstring problems would open the door for his rivals in one of the most eagerly-anticipated races in history.
World champion Yohan Blake made it a Jamaican one-two when he won silver in 9.75 seconds and 2004 Olympic champion Justin Gatlin of the US grabbed bronze in 9.79 seconds, as the first seven men all broke the 10 second barrier.
Bolt now stands alongside Carl Lewis as the only two men with two 100 metres golds, though the American's second in 1988 came only after race winner Ben Johnson of Canada was disqualified for doping.
"After the semi-finals I was really confident because my legs felt great, my execution was great so I was really confident in myself," Bolt told reporters.
"I never remembered I was running against the clock until it was 30 metres to go, then 'world record' popped into my head.
"I looked across at the clock but it was too late to do anything about it then. It was the second fastest time in the world, so I am happy."
Jamaicans back home and in London celebrated their hero's victory.
Danny Ras, a London resident, said: "He represents the power that we hold, and it seems to be hidden a lot of the time. We've got a power; we've got an inner strength that can't be taken sometimes.
"World records, consistent winning the race, it's something that just can't be taken. So we're working with that, it's our strength, we have to back it and support him with it."
For Jamaica the timing was perfect, as the Caribbean nation celebrates 50 years of independence from Britain.
One fan outside a bar Bolt owns in Kingston, the capital, said: "Elated for him, so that's the reason I came to his place, to celebrate the moment, a wonderful moment for Jamaica's fiftieth."
Asafa Powell pulled up with a groin injury near the end of the run to ruin a potential Jamaican sweep of the medal positions.
Blake's time equalled his personal best, while Gatlin beat his. Tyson Gay finished fourth in a season's best 9.80 seconds with fellow American Ryan Bailey fifth in an equal personal best of 9.88 seconds.
The night, however, was all about Bolt, who had said repeatedly that he needed back-to-back titles to cement his place among the sport's "legends".
Having been disqualified for a false start in last year's world championships final, Bolt was never going to risk a flying getaway but he was into his running quickly and up with his key rivals within a few metres.
"I was slightly nervous before I came out but after the cheer that I got when they were introducing me, all those jitters went away. I was like this is it, this is game time," Bolt said.
"'Remember I told you,' my coach said, 'Stop worrying about your start, the best of your race is at the end, that's where you rule'. So I stopped worrying about the start and I executed, so it worked."
Blake, who beat him in the Jamaican trials, Gatlin, back in the mix after serving a doping ban, and Powell were all going well but they needed clear air to have any chance of an upset.
His face scrunched in concentration, Bolt overhauled them soon after halfway and the Jamaican, the rest of the field and 80,000 roaring fans knew it was over.
He crossed the line with his eyes on the clock, his face revealing a look more of relief than joy, before he pointed to the sky and carried on at almost full pace round the bend to soak up the adulation of the delirious crowd.
Bolt will now bid to complete an unprecedented double-double by retaining his 200 metres title and will also seek a sixth Olympic sprint gold in the 4x100 metres relay.
Running with him then will be Blake, whose rivalry with his teammate, friend and training partner could keep athletics fans drooling for years.
"Usain knows what it takes, he is a world beater and he is the fastest man in the world," said Blake. "But I got a medal in my first Olympic Games and a lot of that is down to Usain and our coach."