Kenya's Kelvin Kiptum has shattered the men's marathon world record, winning in two hours, 35 seconds in Chicago to beat compatriot Eliud Kipchoge's previous mark by more than 30 seconds.

Kiptum smashed the London Marathon course record earlier this year and was determined to make magic again in the Windy City as he sped up through the 35-kilometre mark before thrusting his arms in the air to cheers from the crowd down the final stretch.

He had not gone into the race targeting the record but said he knew that twice Olympic champion Kipchoge's previous mark of 2:01:09 was within reach in the final kilometres.

"I feel so happy. I wasn't prepared," he said at the finish line. "A world record was not in my mind today."

The 23-year-old broke the tape three minutes and 27 seconds ahead of compatriot Benson Kipruto, while Belgium's Bashir Abdi finished third in 2:04:32.

Kiptum and fellow Kenyan Daniel Mateiko broke away from the rest of the pack by the 10-kilometre mark and the pair were more than one-and-a-half-minutes ahead of the rest of the field by the halfway point.

Running in only his third marathon, Kiptum made it a one-man race at 35 kilometres, deciding to take advantage of Chicago's famously flat course as he shifted into another gear.

"I saw the time in front of me, I said, 'Let me try - maybe I can run under 2:00'," he said.

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

Kiptum glided through the finish line, seemingly with energy to spare as he leapt into an embrace with race director Carey Pinkowski.

There was also a remarkable effort in the women's race, as Dutch middle-distance runner Sifan Hassan thwarted Kenya's Ruth Chepngetich's bid for a third straight Chicago title in 2:13:44, the second-fastest women's marathon time ever.

Hassan picked up a pair of medals at the World Athletics Championships in Budapest in August and showed no signs of fatigue in Chicago as she broke the tape one minute, 53 seconds ahead of Chepngetich.

Ethiopia's Alemu Megertu finished third in 2:17:09.