Michael Phelps stormed to victory in the men's 200m freestyle swimming, claiming his third gold medal and third world record of the Beijing Olympics.
Phelps, 23, finished nearly two seconds ahead of South Korea's Park Tae-hwan in a time of one minute 42.96 seconds.
The American owned the previous record of 1:43.86 and now has a joint-record nine Olympics career golds.
Phelps's compatriot Peter Vanderkaay took bronze, while Britain's Robbie Renwick finished eighth.
"I just wanted to be out on my own which I had done by the 100 metres mark, that was my goal," said Phelps, who led from start to finish.
"I was out in open water and I was in the middle, which makes it difficult for the other guys to see me.
"I knew Park would have a strong last 50 metres, so I had to keep my focus and concentration."
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Phelps has already triumphed in the 400m individual medley and 4x100m freestyle relay and looks to be improving with each race.
The 200m freestyle has a medal which eluded him in Athens when he was a bronze medallist behind Australian Ian Thorpe.
"Phelps swam so fast," said silver medallist Park. "It is my honour to compete with him."
Phelps's ninth career Olympic gold draws him level with Mark Spitz Carl Lewis, Paavo Nurmi and Larysa Latynina and keeps him on course to beat Spitz's 36-year-old record of seven golds in a single Games.
Racing out of lane six, Phelps quickly surged into the lead and led by a full body length halfway through the second of four lengths.
Phelps will race for his fourth medal on Wednesday in the 200m butterfly, yet another event in which he holds the world record.
He advanced to the final as the fastest qualifier just moments after receiving his 200m freestyle gold medal.
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