Kelvin Kiptum set the world record at the Chicago Marathon in October, 2023 with a time of 2:00:35, beating the record of 2:01:09 set by compatriot Eliud Kipchoge in Berlin in 2022. He improved his personal best time by 50 seconds to beat the 2:01:09 record set by fellow Kenyan Eliud Kipchoge, who is widely considered the greatest marathoner of all time. Kiptum was widely believed to be the successor to Kipchoge, and a possible contender to run the marathon in under 2 hours.
Kiptum made a debut at a World Marathon Major, winning the 2023 London Marathon in what was then the second-fastest time in history of 2:01:25, 16 seconds outside the then-world record.
Kiptum ran the fastest-ever marathon debut at the 2022 Valencia Marathon, becoming the third man in history to break two hours and two minutes. He also became the fastest debutant marathoner in history. He beat the 2022 world marathon champion Tamirat Tola, a pre-race favourite, among others.
Kiptum debuted internationally at the Lisbon Half Marathon in March 2019, finishing fifth with a new personal best of 59:54.
At the age of 18, in October 2018, Kiptum won the Eldoret Half Marathon with a time of 1:02:01.