Kenya's Ruth Chepngetich has put on a performance for the ages as she obliterated the women's marathon world record in Chicago, taking nearly two minutes off the previous best to win in 2 hours 9 minutes and 56 seconds.

Chepngetich ditched the competition by the halfway mark on Sunday and ran through a chorus of cheers through the final straight as she claimed her third title in Chicago and crushed Ethiopian Tigst Assefa's previous record of 2:11:53, set last year in Berlin.

Ethiopia's Sutume Kebede crossed the line seven minutes and 36 seconds later while Kenyan Irine Cheptai (2:17:51) was third.

"This is my dream that has come true," said Chepngetich, whose time was originally recorded as 2:09:57 but was later adjusted by a second.

Her compatriot John Korir won the men's race in 2:02:44.

Chepngetich set a blistering pace from the start, running the first five kilometres in 15 minutes flat and by the halfway mark had built a 14-second cushion between herself and Kebede.

Television commentators were astonished as she grinded through the course, comparing her attempt at a sub-2:10 marathon to the moon landing, and she only seemed to gain momentum as she sprinted through the final two miles.

Chepngetich, the 2019 world champion, hunched over in utter exhaustion after breaking the tape and dedicated her performance to compatriot Kelvin Kiptum, who broke the men's world record a year ago in Chicago and died in a car crash four months later.

"World record was in my mind," she said. "Chicago, as I said in the press, is like home."

The day began with a moment of silence at the starting line for Kiptum, who ran last year in 2:00:35, as runners took off under pristine conditions in the Windy City.

Korir stuck with a crowded men's lead pack through the first 30 kilometres before making his move and was nearly 30 seconds clear of the rest of the field by the 35-kilometre mark.

He glided through the final kilometres, holding his arms out wide as he finished his textbook performance in a personal best time for his first major title.

Ethiopia's Mohamed Esa was second in 2:04:39 while Kenyan Amos Kipruto (2:04:50) finished third.

"Today I was thinking about Kiptum," said Korir. "I had to believe in myself and try to do my best."