Michael Phelps was denied his first gold of the London Olympics as France pipped the United States to win the men's 4x100m relay.
France were behind the reigning Olympic champions heading into the last leg but Yannick Agnel passed Ryan Lochte down the final 100m to triumph.
Russia earned the bronze, while favourites Australia finished fourth.
"France have won two gold medals tonight and they will be absolutely rapt with those performances. I knew that Yannick Agnel would come back and swim well in the final leg and it looks good for him with the 200m freestyle to come.
"I'm feeling the same as the first night when Phelps came fourth and everybody was shocked. Breaking that race down, people in Australia will be terribly disappointed."
Phelps's silver takes his Olympic medal tally to 17 overall, one short of Russian gymnast Larisa Latynina.
The expected duel between the United States and the Australian team of James Magnussen, Matt Targett, Eamon Sullivan and James Roberts never materialised in a pulsating race.
World champions Australia were out of the medal places after the first leg, while Nathan Adrian handed over to Phelps for the second leg for the US.
Phelps established a two-metre lead, which was maintained by Cullen Jones on the third stint, but when Agnel took to the water he clawed back America's lead within 50 metres.
Lochte's turn into the final length re-established the US in the lead, but Agnel burst past him in the final 15 metres to seal a stunning victory for the team of Amaury Leveaux, Fabien Gilot, Clement Lefert and Agnel.
The French - who lost out in Beijing by 0.08 seconds in 2008 - won gold in 3:09.93, with the US second in 3:10.38 and Russia third in 3:11.41.
Final results by Country
View full results for Men's 4 x 100m Freestyle Relay
Leveaux, Gilot, Lefert, Agnel, Bernard, Stravius
Adrian, Phelps, Jones, Lochte, Feigen, Grevers, Berens, Lezak
Grechin, Lobintsev, Morozov, Izotov, Lagunov, Fesikov