The world's fastest man, whose imperious performances in London have blown away any doubts that he deserves the unofficial title of greatest ever sprinter, stopped the clock at 19.32 seconds, the joint fourth quickest time ever run.
Bolt holds the world record in his "pet" event with an eye-popping 19.19 at the Berlin world championships in 2009.
The showman again put compatriot and younger rival Yohan Blake, the pretender to his sprint throne, firmly in place and has now matched his stunning Beijing 100 and 200 crowns four years ago following his shorter-dash victory on Sunday.
Blake, as he did in the 100 behind his friend and training partner, took silver in 19.44 and Warren Weir completed a Jamaican podium sweep with bronze in 19.84. All three share the same coach - Glen Mills.
Bolt crossed the line with his finger to his lips before doing a handful of press-ups on the track. Then, taking a photographer's camera, he took snaps of the crowd and Blake who was posing as "The Beast", the nickname Bolt afforded his rival.
"I've got nothing left to prove. I've showed the world I'm the best," said the athlete who has lit up track and field since turning his prodigious talent into global dominance.
"This is my moment. I'll never forget this. I did what I wanted. I came out of a rough season and did what I had to do."
The 25-year-old, who came into the Games with lingering doubts over his fitness after a far from vintage season, was the first man to win two 200 Olympic golds and, as he did in 2008, he will look to complete the treble in the 4x100 relay.
Bolt said his finger gesture as he crossed the line was to silence the doubters.
"That was for all the people that was doubting me. All the people that was talking all kinds of stuff that I wasn't going to do it," he said.
"I was not going to be beaten. All this stuff. You can stop talking now because I am a legend."
Bolt's winning time matched that of American Michael Johnson who set a then world record of 19.32 to win Olympic gold in Atlanta in 1996.
Bolt lowered that to 19.30 in Beijing before his 19.19 a year later.
On a warm and windless evening with the electric atmosphere inside an expectant Olympic stadium raised by Kenyan David Rudisha's 800m world record, Bolt, relaxed and smiling in the preliminaries, flew out of the blocks.
Drawn towards the outside in lane seven, Bolt glided around the bend and kicking powerfully down the home straight was always ahead of Blake who could not match his exploits in the Jamaican trials when he beat Bolt in both sprint events.
Bolt said his defeats in Kingston had been a "wake-up call", although he admitted that he was not quite 100 per cent fit in London.
"I'm not feeling 100 (per cent) but I'm definitely close to 100 percent," he said.
"I came here a little bit off but I was ready and focused."
Bolt said Blake had "really pushed him this season" and that his time (to be champion) was not far away.
A beaming Blake, 22, was just happy to bask in Bolt's limelight.
"I can't complain...it's a double silver for me.... I beat him at the trials and he wanted to get me back. Definitely he's a legend. This is his time but my time will come."
Weir edged Wallace Spearmon for third but the American hailed the performances of Bolt and Blake.
"Those guys are on another plant right now, congratulations," said fourth-placed Spearmon, hiding his disappointment at again missing out on a medal after being disqualified from third place in Beijing for stepping out of his lane.
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