Farah, 31, who was running his first competitive marathon, finished in eighth place. He also missed out on breaking the British record.
Wilson Kipsang from Kenya won the event in a new course record. Stanley Biwott came second and Tsegaye Kebede third.
Kenya's Edna Kiplagat won the women's elite race with Florence Kiplagat in second and Tirunesh Dibaba third.
Continue reading the main story Olympian Mo Farah missed out on breaking the British record of 2:07:13Men's winner Wilson Kipsang set a new course record of 2:04:29 - 11 seconds faster than Emmanuel Mutai in 2011 Kenya's Edna Kiplagat won the women's elite race in 2:20:2136,000 fun runners are taking on the routeWorld record holder Kipsang crossed the line in a time of two hours, four minutes and 29 seconds.Farah - the Olympic and world champion at both 5,000m and 10,000m - had been the bookies' favourite to win the event.
He had also aimed to beat Steve Jones' British record of 2:07:13 seconds which has stood since 1985 - but missed out by finishing in 2:08:21.
After the race he told the BBC: "I will be back. I gave it a go but I'm disappointed I didn't give a bit more than the crowd deserved.
Sharon, Karen, Debbie & Penny will be carrying Colin the War Horse for The Royal British Legion "It was the strongest field ever brought together by the London Marathon. It would have been wrong to do any other marathon. This is my hometown."
Steve Jones said Farah's first competitive marathon was "extremely good" and he was "honoured not to have my record broken".
After the race men's winner Kipsang, said: "I was feeling good and took advantage of controlling the pace and controlling the guys."
The other Britons who finished the men's elite race were Scott Overall, Craig Hopkins and debutants Chris Thompson and Ben Livesey.
In the women's race, British runners Amy Whitehead and Emma Stepo finished in 13th and 14th places with times of two hours, 34 minutes and 20 seconds and two hours 36 minutes and five seconds.
Britain's David "Weirwolf" Weir lost his bid to become the best wheelchair racer in the event's history.
He had been aiming to win his seventh title but was beaten into second place by Switzerland's Marcel Hug.
American Tatyana McFadden took the elite women's wheelchair race title, a month after winning a silver medal at the Winter Olympics for cross-country skiing.
Visually impaired athletes and their guides set off in the IPC Athletics Marathon World Cup race Game of Thrones Legions of fun-runners taking part in the event are raising thousands of pounds for charity.
Celebrities including former Liverpool and England footballer Michael Owen, Game of Thrones actress Natalie Dormer, and Michelin-star chef Michel Roux Jr are just some of those that have taken up the challenge.
Nine MPs are also tackling the course with Shadow Chancellor Ed Balls running his third consecutive London Marathon.
Tony Phoenix-Morrison is carrying a fridge Sisters Katie, 23, and Polly Ryall, 21, from Newbury, Berkshire, are aiming to become the fastest pair of female siblings to run a marathon.
Their combined time for crossing the finish line needs to be under the current world record of five hours, nine minutes and 14 seconds.
Katie said: "We're hoping to break the record but, failing that, we are both just looking to beat each other."
Race starters Grainger and Watkins, who won the women's double sculls gold at the London 2012 Games, are two of 13 London Olympics gold medallists taking on the famous course from Blackheath to The Mall.
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Olympic stars to start marathon