American Nathan Adrian edged Australian sprint powerhouse James Magnussen by one one-hundredth of a second to win the men's 100m freestyle swimming gold at the London Olympics.
Adrian, who came into the Games lagging behind Magnussen in the world rankings, clocked 47.52sec to hand the Aussie another crushing defeat after Australia's failure to medal in the 4x100m freestyle relay.
Magnussen took silver in 47.53 and Canada's Brent Hayden earned bronze in 47.80 in just one of the night's thrillers at the Aquatics Centre.
Hungarian Daniel Gyurta got the evening off to a rollicking start with a world record victory in the men's 200m breaststroke.
The two-time world and European champion had seized the lead from two-time defending Olympic gold medallist Kosuke Kitajima by the final turn and stormed home with Britain's Michael Jamieson pushing him all the way.
The duel sent the crowd into a frenzy, but it was Gyurta's gold in 2:07.28.
Jamieson took silver in 2:07.43 and Japan's Ryo Tateishi sneaked past the fading Kitajima to claim bronze in 2:08.29 - a full second adrift.
"It was a really hard race," Gyurta said. "In the last 20m I saw Jamieson, he was so fast in the last part. It was hard for me, but I managed to do it."
Kitajima, who came into the Games with the fastest 200m time in the world this year, saw his Olympic breaststroke reign ended in a fourth place finish. He had already finished fifth in the 100m breaststroke won in a world record by South African Cameron van der Burgh.
US superstar Michael Phelps meanwhile finished second in a head-to-head semi-final clash with team-mate Ryan Lochte in the 200m individual medley.
Phelps returned to the pool a day after a 200m butterfly silver and relay gold gave him a record 19 career Olympic medals.
Lochte had a busy night, the 200m medley semis coming after he he won his 200m backstroke semi to secure his spot in the final with the second-quickest time of the night.
China's Jiao Liuyang won the women's 200m butterfly, four years after settling for silver in Beijing behind team-mate Liu Zige.
Now the world champion, Jiao used a strong second 100m, running down Spain's Mireia Belmonte Garcia to win in an Olympic record of 2:04.06.
Belmonte Garcia settled for silver in 2:05.25 with Japan's Natsumi Hoshi third in 2:05.48.