Brigid Kosgei has broken the marathon world record at the Chicago Marathon.
She clocked 2:14:04, beating the record set by Paula Radcliffe in London in 2003 by one minute and 21 seconds.
Radcliffe was there to see her mark, and her Chicago course record from 2002, eclipsed by the 25-year-old Kenyan.
Kosgei said, "I am feeling good and I was happy because I was not expecting to run like this. People are cheering and I get more energy and the morale to kick and keep kicking. I am happy again for the people of this place.
"When I was going, I could feel my body moving, moving, moving. So I tried to go." - Brigid Kosgei speaking on the road after her world record run
Kenya's dream weekend
The pair were victorious in London in April with both electing to skip the IAAF World Championships.
Assisted by male pacemakers, as Radcliffe was 16 years ago, Kosgei set a breakneck speed from the outset going through the first 5km in 15:28.
She reached the midway point in 1:06:59, over a minute quicker than Radcliffe's half-marathon split.
Despite appearing to struggle around the 30km mark, Kosgei managed to keep up the tempo and crossed the line to complete a superb weekend for her country's long-distance runners.
She took more than four minutes off her previous best of 2:18:20 set in her London triumph.
Speaking afterwards while stood next to the new world record holder, Radcliffe said of Kosgei's early pace, "If she was able to hold it together she was always going to beat the time.
"I guess for me 17 is my lucky number, and it was exactly 17 years to the day that I set the first world record here in Chicago. That was a very special day and it's a very special day for Brigid today."
Kosgei completed a double for Kenya after Lawrence Cherono had won the men's title, adding to his victory in April's Boston Marathon.
Cherono outsprinted subsequent world champion Lelisa Desisa in Boston, and he again showed his strength in a finish here.
The 31-year-old got the better of Ethiopian pair Dejene Debela and Asefa Mengstu to take victory in 2:05:45.
Defending champion and four-time Olympic track gold medallist Mo Farah lost touch with the lead group before halfway and finished eighth, while Rio 2016 marathon bronze medallist Galen Rupp dropped out after 35km in his first race since surgery on an Achilles tendon.
Romanchuk and Schaer retain wheelchair titles
Daniel Romanchuk was the first winner on Sunday, scoring a comfortable win in the men's wheelchair event.
The 21-year-old from Maryland came home in 1:30:26, just over three minutes clear of Britain's David Weir who beat South Africa's former winner Ernst van Dyk and another Briton, Johnboy Smith, in the sprint for second.
Meanwhile, Manuela Schaer continued her dominance in women's wheelchair races with an even more emphatic victory.
The Swiss has now won eight consecutive marathon majors after completing a Grand Slam of the six events last season.
She finished in 1:41:08, more than four minutes clear of home favourite and eight-time winner Tatyana McFadden with three-time former champion Amanda McGrory seven seconds further back in third.