While Kipsang led a Kenyan one-two in the men's race, defending London champion Keitany spearheaded a medal sweep in the women's - the first ever for women in London. Indeed, Kenyans filled the first five places.
Keitany made the most of perfect conditions to kick away from a clutch of highly talented rivals in the last four miles before powering home in 2:18:37, which is an African record, improving the mark of compatriot Catherine Ndereba, who had run 2:18:47 back in 2001.
Keitany's time is also a world leading time this year, making her the third quickest woman of all time and the fifth fastest ever.
"The time was OK," she said. "The weather here all week has not been good but when I saw the sunshine this morning I knew it would be all right for me."
Keitany and World champion Edna Kiplagat both passed the 35K point in 1:56:01, a sub 2:20 pace, putting them in pole position for fighting for Olympic qualification.
Kiplagat challenged the defending champion until 23 miles and maintained her form over the closing miles to record her first sub-2:20 time, crossing the line in 2:19:50, a personal best by nearly a minute.
There was a lifetime best for third place Priscah Jeptoo too, the world silver medalist running 2:20:14, more than two and half minutes inside her previous best. Other Kenyans Florence Kiplagat (2:20:57) and Lucy Kabuu (2:23:12) finished fourth and fifth place respectively.
Earlier in the race, Ethiopian Ejegayehu Dibaba dropped out before the 10K mark.
Wilson Kipsang missed Emmanuel Mutai's course record on his London debut by just four seconds
Kipsang came to London as the second fastest man in history and he stamped his authority on a heavily loaded field with two bold surges in the second half of the race.
Breaking free after 33K, the two-time Frankfurt Marathon champion crossed the line more than two minutes clear in 2:04:44 followed by Martin Lel (Kenya) - the three-times London champion repeating his second place from 2011.
"I knew when I went away they would have to work very, very hard to beat me as I was feeling so good in myself," said Kipsang.
"I am so sorry I didn't ditch the record but winning is the most important thing for me. I feel little tired now, but I am happy and tired."
By the 40K mark, World Champion Abel Kirui was on course for second place after passing the mark in 1:59:23 and was 33 seconds ahead of Ethiopian Feyisa Lilesa. However, there was a late drama as Abel Kirui faded badly on the final few kilometres and dropped back into sixth (2:07:56).
Lel came through for second position in 2:06:51 winning a sprint finish by a second from Ethiopia's Tsegaye Kebede (2:06:52).
Moroccans Adil Annani (2:07:43) and Jaouad Gharib (2:07:44) finished in fourth and fifth places respectively with defending champion Emmanuel Mutai (Kenya) finishing seventh (2:08:01).
Lilesa ended up in tenth clocking a disappointing time of 2:08:20 and World record-holder, Patrick Makau from Kenya dropped out of the race throwing his Olympic selection in doubt.
Selected Top Results
1. Wilson Kipsang KEN 2:04:44
2. Martin Lel KEN 2:06:51
3. Tsegaye Kebede ETH 2:06:52
4. Adil Annani MAR 2:07:43
5. Jaouad Gharib MAR 2:07:44
6. Abel Kirui KEN 2:07:56
7. Emmanuel Mutai KEN 2:08:01
8. Marilson Gomes dos Santo BRA 2:08:03
1. Mary Keitany KEN 2:18.37
2. Edna Kiplagat KEN 2:19:50
3. Priscah Jeptoo KEN 2:20:14
4. Florence Kiplagat KEN 2:20.57
5. Lucy Kabuu KEN 2:23:12
6. Aberu Kebede ETH 2:24:04
7. Irina Mikitenko GER 2:24:53
8. Jessica Augusto POR 2:24:59
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