The men's marathon world record holder, Kenya's Kelvin Kiptum, 24, has died in a road accident in his home country.
He was killed alongside his coach, Rwanda's Gervais Hakizimana, in a car on a road in western Kenya on Sunday.
Kiptum made a breakthrough in 2023 as a rival to compatriot Eliud Kipchoge - one of the greatest marathon runners.
Kiptum bettered Kipchoge's record, clocking the 26.2 miles (42km) in two hours and 35 seconds in Chicago last October.
The two athletes had been named in Kenya's provisional marathon team for the Paris Olympics later this year.
Kipchoge said on X that the man who broke his record was a rising star who had "a whole life" ahead of him to achieve "incredible greatness", offering condolences to his family.
Also paying tribute, Kenya's President William Ruto described Kiptum as an extraordinary sportsman who had left a mark on the world.
The road accident happened at about 23:00 local time (20:00 GMT) on Sunday.
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Giving details of the crash, police said Kiptum was driving and had "lost control [of the vehicle] and veered off-road entering into a ditch on his left side".
"He drove in the ditch for about 60 metres before hitting a big tree," a police statement said.
Kiptum and Hakizimana died at the site of a collision. A third person - a young woman - was seriously injured and taken to hospital for treatment.
Just last week, Kiptum's team announced that he would attempt to run the marathon in under two hours in Rotterdam in April - a feat that has never been achieved in open competition.
The rise to fame for the father-of-two had been rapid - he only competed in his first full marathon in 2022.
He made an instant impact as he ran the then fourth fastest time on record (2:01:53) to win the Valencia Marathon before setting a course record of 2:01:25 at the London Marathon in April 2023.
Six months later, in just his third marathon, Kiptum took 34 seconds off the world record time in Chicago in his final race.
He had already honed a distinct tactical approach that saw him run with the pack for 30km before upping the pace and going out on his own for the remainder of the race.
Kiptum entered his first major competition in 2018, running in borrowed shoes because he could not afford a pair of his own.
He was among a new crop of Kenyan athletes who began their careers on the road, breaking away from the past tradition of athletes starting on the track before switching to longer distances.
Kiptum told the BBC last year that his unusual choice was simply determined by a lack of resources.
"I had no money to travel to track sessions," he explained.
People have gathered outside the hospital in the Rift Valley town of Eldoret where his body has been taken.
"I don't know what to say but God, if we have done wrong, God forgive us because Kiptum was headed for great heights," one man said.
"We want to say very sorry to the Kenyans and much more to the family of the departed hero. Very sorry," another told a local TV channel.
Reacting to the news of his death, Kenyan Sports Minister Ababu Namwamba wrote on X: "Devastatingly sickening!! Kenya has lost a special gem. Lost for words."
Kenya's opposition leader and former prime minister, Raila Odinga, said the country had lost "a true hero" and was mourning "a remarkable individual... and Kenyan athletics icon".
And Sebastian Coe, the president of World Athletics, said Kiptum was "an incredible athlete leaving an incredible legacy".
Kiptum's coach, Hakizimana, 36, was a retired Rwandese runner. Last year, he spent months helping Kiptum target the world record.
Their relationship as coach and athlete began in 2018, but the pair first met when the world record holder was much younger.
"I knew him when he was a little boy, herding livestock barefooted," Hakizimana recalled last year. "It was in 2009, I was training near his father's farm, he'd come kicking at my heels and I would chase him away.
"Now, I am grateful to him for his achievement."
