Michael Phelps won his first individual gold at London 2012 and his 20th Olympic medal by beating Ryan Lochte in the men's 200m individual medley.
The American led from the front and looked as if he might break the world record but touched for a historic 16th gold medal in 1:54.27.
Phelps also becomes the first man to defend an Olympic swimming title twice, having won in Athens and Beijing.
Hungary's Laszlo Cseh was third, while Britain's James Goddard was seventh.
"I tried to go for it and paid for it down the back but it's a been a fantastic experience," Goddard told BBC Sport.
Lochte, 27, was made to pay for entering the men's 200m backstroke final, which finished roughly half an hour before this race.
In the earlier distance he finished third, but his silver behind Phelps means he has won two golds and five medals in all at London 2012.
Phelps, 26, has now won two golds and two silvers at the Aquatics Centre and beat Lochte in this instance by 0.63 seconds.
Goddard clocked a time of 1:59.05.