In only his third marathon Kiptum, 23, took 34 seconds off the mark set at last year’s Berlin Marathon by his 38-year-old compatriot Eliud Kipchoge - whose prospects of earning a third consecutive Olympic title in Paris next summer look suddenly less secure.

Kiptum’s achievement came just a fortnight after a similarly seismic improvement of the women’s world record by Ethiopia’s Tigist Assefa, who took more than two minutes off the mark of 2:14:04 set at the 2019 Chicago Marathon by Kenya’s Brigid Kosgei as she won in Berlin in 2:11.53.

Hassan, 30, who has won two world and two Olympic track titles for The Netherlands, was running only her second marathon after winning the London race in April in 2:18:33.

In between those races she added to her track CV by winning the 5,000m silver and 1500m bronze at the World Athletics Championships in Budapest.

Kiptum, who ran the fastest marathon debut time in Valencia last year - 2:01:53 - and won the London Marathon in 2:01.25, the second fastest time ever, finished in jubilant fashion, waving and blowing kisses to the crowd.

"A world record was not in my mind today," he told reporters.

"But I knew one day, one time I would be a world record holder.

"Now I am very happy."

Kiptum was four seconds inside world record pace as he went through 10 kilometres in 28min 42sec and passed the halfway mark in 60:48, with only compatriot Daniel Mateiko in contact.

He has now become the second fastest man ever over the distance after Kipchoge’s clocking of 1:59:40 in Vienna four years ago.

That did not qualify as an official world record as it was not an open event - Kipchoge was handed fluids by his support team throughout and the run featured a pace car and included rotating teams of other runners pacing him in a formation designed to reduce wind resistance.

It is understood that both winners were wearing the latest Nike super-shoe, the Alphafly 3, which will become generally available early next year.

Assefa won her race in Berlin in a newly-designed adidas super-shoe, the Adizero Adios Pro Evo 1, reportedly a single-use shoe now retailing at $500 (£400/€470).

Kiptum's run in cool and cloudy conditions marked the third time a men's world record had been set on the streets of Chicago but the first time since Morocco's Khalid Khannouchi in 1999.

"I saw the time in front of me," he said. 

"I felt good inside of me, maybe a little adrenaline."

Beforehand he had targeted the course record of 2:03:45, set by Kenyan Dennis Kimetto in 2013.

"Chicago is a flat course," Kiptum said.

"I thought I'd go and try Chicago."

Kenyan Benson Kipruto, the defending champion, was a distant second in 2:04:02 with Belgium's Bashir Abdi, the European record-holder and Tokyo 2020 bronze medallist, third in 2:04:32.

Hassan’s triumph frustrated the ambition of Kenya’s 2019 world champion Ruth Chepngetich, whose winning time of 2:14.18 last year was second only to the then world record, to earn a third consecutive victory in the Windy City.

Chepnegetich was six seconds ahead of her Dutch rival at the halfway point, and at halfway, passed the mark in 65:42, which was 2:11:23 pace.

Hassan moved clear between 25-30km before finishing weary but triumphant.

"As most people know, I like to be challenged," she had said before the race.

Point made, once again.

"I ran so great. I'm so happy," Hassan said afterwards.

 "I ran an amazing time. 

"I never thought I'd run 2:13.

"It's unbelievable."

Chepngetich finished second in 2:15:37 - 1:53 behind Hassan -  with Ethiopia's Megertu Alemu third in 2:17:09 and Kenya's Joyciline Jepkosgei, the 2019 New York Marathon and 2021 London Marathon winner, fourth in 2:17:23.

Earlier in the day Swiss wheelchair racers Marcel Hug and Catherine Debrunner set new course records for the men’s and women’s events.