Farah, the world and Olympic 5,000 and 10,000 metres champion, was given a "tough" baptism by the world's best - finishing almost four minutes behind world record holder Kipsang on a sunny morning in the capital.
The 32-year old Kenyan claimed a second London title with a course record two hours four minutes 29 seconds, pulling clear of compatriot Stanley Biwott who was 26 seconds back with Ethiopian Tsegaye Kebede third.
"The pacemakers went too early for me so I had to push myself," said Kipsang who also won in 2012, the same year he won Olympic bronze around the streets of London.
"At around 31k I decided to push harder as I felt very comfortable and strong. And then I pushed again towards the finish line and that was when I broke away."
Farah, who was never in contention after dropping behind the leaders from the start, gritted his teeth to cross in 2:08:21, outside the British record that has stood since 1985.
"That was tough. I'm very disappointed," said a chastened Farah.
"I didn't really know what to expect. Training went well. The crowds were exciting and really helped me along.
"It was a little bit windy and I didn't really have a plan. I'll definitely be back."
Edna Kiplagat won her first London title after finishing runner-up in the past two years, getting the better of compatriot Florence Kiplagat in the final 200 metres to win in two hours, 20 minutes and 21 seconds.
The winner outkicked her namesake who finished three seconds behind after the pair had dropped debutant Tirunesh Dibaba, stepping up from the track where she enjoyed a glittering career.
"Towards the end of the race I tried to push a few times but she was always there," Edna Kiplagat, who retained her world title in Moscow last year, said of her battle with the world half-marathon record holder.
"I felt strong so I wasn't too worried."
Ethiopian Dibaba, a three-time Olympic track champion, was still in contention when she blundered at a drinks station, stopping to pick up her dropped water bottle and losing valuable time on the front pair.
"When my bottle fell, I tried to pick it up because it's important to me," she said after finishing third, 14 seconds behind the winner.
"That made me lose lots of time with the lead runners. I was feeling pretty good but it's difficult to lose so much time against top athletes."
Last year's London winner Priscah Jeptoo dropped out of the race at around the 25-km mark while Olympic champion Tiki Gelana finished ninth.
- Athletics, Track & Field
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- Edna Kiplagat