Ethiopia's Tiki Gelana won gold in the London 2012 women's marathon in an Olympic record time of two hours, 23 minutes and seven seconds.
Kenya's Priscah Jeptoo claimed silver, five seconds behind, while Russia's Tatyana Petrova Arkhipova took bronze.
Freya Murray, a
late replacement for injured Paula Radcliffe,
was the best placed Briton, 9:07 back in 44th place.
Team-mate Claire Hallissey was more than 12 minutes behind in 57th, while Mara Yamauchi quit just before 10km.
In winning on The Mall, 24-year-old Gelana took seven seconds off the previous Olympic record as she sprinted to victory ahead of Jeptoo.
Petrova set a personal best of 2:23:29, while Kenya's Mary Keitany, winner of the London marathon this year, had to settle for fourth after being dropped by the leading pack in the final stages.
"I'm not sure many people would have tipped Gelana," said BBC commentator and former Olympic 1500m silver medallist Steve Cram.
"The crowd on The Mall roared the Ethiopian Tiki Gelana home. She showed in Rotterdam earlier this year when she broke the Ethiopian record that she could run a fast time. This time she did it on the Olympic stage. The pre-race favourite, Kenya's Mary Keitany, was almost jogging at the end as her dream of winning the Olympics was taken away."
"She wasn't quite unknown, but to run in such a way was impressive. She looked really relaxed until the last 200m-300m, when she strained to reach the finish line.
"Once again, the Kenyans have had to play second fiddle to the Ethiopians, who were dancing with joy at the end."
Murray, 28, was the first Scottish woman to represent Britain in an Olympic marathon since Liz McColgan at Atlanta in 1996.
She says she is now targeting the Commonwealth Games and then the Rio Games in 2016.
"It was a brilliant experience for me and, hopefully, a stepping stone to Glasgow 2014 and Rio 2016," she said.
"When I got the call last Sunday, I was devastated for Paula but excited. I feel I have justified my selection."
Yamauchi, 38, was sixth in the 2008 Beijing Olympic marathon but has since struggled with injury.
She said: "I had a heel bruise that I thought I was able to run on. I was confident I could give it a go, but on the second corner it started hurting.
"I did my best and it is not good to drop out in your home Games. I didn't want my Olympic journey to end like this. I thought about withdrawing beforehand and had much higher hopes. Sadly it wasn't to be."