Eliud Kipchoge has become the first marathon runner to break the two-hour barrier, recording a time of 1 hour 59 minutes 40 seconds in Vienna.
He had previously pushed the mark close in a similar attempt at the Monza Formula One racetrack near MIlan in 2017.
Kipchoge ran 2:00:25 on that occasion, but added extra pacemakers and allowed fans to line the streets for this attempt, as he made sporting history in Austria.
A reminder: The sport's governing body, the IAAF, will not recognise the run as an official record because it is not in open competition and it uses in and out pacemakers.
Kipchoge, 34, the reigning Olympic champion who set an official world record of 2:01.39 at the Berlin marathon in September last year, missed out by 26 seconds when he previously attempted to break the two-hour barrier in Monza in May 2017, a race run without spectators.
Kipchoge is on target in his bid to run an unofficial sub-two hour marathon as he completed the first half of his attempt at Vienna's Prater Park.
The 34-year-old marathon world record holder completed the first 21 kilometres in 59.35 minutes, 11 seconds under the two-hour pace.
However, there were a few spots of rain which had not been expected and which could hamper his attempt.
Kipchoge continues: "Absolutely remember the 41 pacemakers are among the best athletes ever in the world.
"I can say thank you to them, I appreciate them for accepting and together we made history on this one.
"We can make this world a beautiful world and a peaceful world. My wife and three children, I am happy for them to come and witness history.
"The positively of sport, I want to make it a clean sport and an interesting sport."
In jubilant scenes Kipchoge was somehow able to keep running as he celebrated with the crowd before being hugged by his INEOS team-mates.
Kipchoge's coach, Patrick Sang, has praised the Kenyan for 'inspiring the world'.
"He has inspired all of us that we can stretch our limits in our lives," he said. "You have made history.
"Everything went perfectly right. For the sport, it challenges other young athletes. For humanity, whatever level you are in you can move yourself to another level.
"Records are meant to be broken, so down the line someone will try again, but history has been made. It's unbelievable."
Eliud Kipchoge has become the first runner to finish a marathon in under two hours.
The 34-year-old Kenyan completed the course in Vienna, Austria, in an incredible one hour, 59 minutes and 40 seconds.
Kipchoge was racing alone but assisted by 41 pacemakers, including former Olympic and world record holders, in his attempt to achieve the milestone.
The time will not be an official world record but is nonetheless a historic moment in distance running.
The INEOS 1:59 Challenge was Kipchoge's second shot at the record after missing out by 25 seconds in his first attempt in Monza two years ago.
Kipchoge was even able to wave to the crowds as he sprinted towards the finish line, where his wife Grace greeted him.
In jubilant scenes Kipchoge was somehow able to keep running as he celebrated with the crowd before being hugged by his INEOS team-mates.
Afterwards he told the BBC: "I am feeling good. After Roger Bannister in 1954 it took another 63 years, I tried and I did not get it.
"After 65 years, I am the first man! I want to inspire many people, that no human is limited."
Here are the numbers behind the Kenyan’s incredible achievement.
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Who is Kipchoge?
Kipchoge is perhaps the best candidate in the world to attempt such a historic achievement in breaking the two-hour barrier for the marathon.
A four-time champion of the London marathon, having won the last two editions, as well as a two-time winner in Berlin and a solitary victory in Chicago to go with his Olympic gold medal.
What is the 1:59 challenge?
Ineos have sponsored the event, which will take place around the 4.3km stretch on the Prater Hauptallee in Vienna, Austria, with 4.4 laps required to complete the marathon distance.
Elevation will remain comfortably flat, though it will fluctuate between 1.8 and 4.0 metres. One request of Kipchoge since Nike Breaking2 was to involve fans, meaning the route will be lined by spectators in order to provide him with support.
