Ranomi Kromowidjojo claimed her first gold medal at London 2012 with victory in the women's 100m freestyle.
The Dutch swimmer clocked an Olympic record of 53.00 seconds to finish ahead of Aliaksandra Herasimenia of Belarus, while China's Tang Yi won bronze.
Kromowidjojo, 21, was favourite going into the race after setting an Olympic record in the semi-final with 53.05secs.
"Fran Halsall looked good at 50 [metres], she took the race on. It was looking good and generally you can rely on Fran to finish strongly. Her British record would have done enough to win gold in that. The other girls came back at her very strongly."
Great Britain's Fran Halsall touched the wall in sixth place.
"I just didn't have it today. I can't change it now unfortunately, I gave it my best shot," said Halsall, who had been fastest off the blocks.
Great Britain have two medals so far in the pool.
After completing the first lap in fourth place, Kromowidjojo surged on the last length to become the first Dutchwoman to win the classic women's sprint at the Olympics since Inge de Bruijn in 2000.
American teenager Missy Franklin finished out of the medals in fifth place.