The run will start on October 12, at 8.15am in Vienna (7.15pm Saturday, NZ time). The start time can be moved, depending on weather and other logistics, to any time between October 12 and October 14.
Kipchoge left Kenya for Vienna on October 6 and has been in the city since then, preparing for his race.
This is not the first time Kipchoge has attempted to go sub-2.
Fans will remember his previous attempt, in 2017, as part of the Nike Breaking2 project. Back then, he ran around a racetrack in Monza, Italy, and came within seconds of breaking the illusive barrier, running the fastest marathon in history, in 2:00:25.
Despite having previously fallen short of his ultimate goal, the Kenyan runner is confident he can do it today.
If he breaks sub-2, the run will not be eligible for an official world record, because of the conditions he will have for it (namely, his rotating set of pacers).
Back in August, he told Runner's World that getting an official record is not why he's doing this.
"This is about history, it's about leaving a legacy. It's about inspiring people. It will mean a lot when I run under two hours," he said.
In any case, Kipchoge already holds the official record for the fastest marathon in the world anyway. The 34-year-old ran the Berlin Marathon last year in 2:01:39, taking 18 seconds off the previous world record.
A few months later, proving he is still in peak form, in April this year, he ran the London Marathon in his second-fastest marathon time of 2:02:37, winning the race outright.
Kipchoge is as ready as he can be for this extraordinary attempt. Three hours ago, he posted a close-up shot of his face on Instagram with the caption: "I don't know where the limits are, but I would like to go there."
All you need to know
What: INEOS 1:59 Challenge is the name of the run Kipchoge will do to try to break the sub-2h barrier for the marathon.
When: Saturday, October 12. The event is scheduled to start at 8.15am in Vienna (7.15pm in New Zealand).
How to watch: The run will be livestreamed on YouTube. The stream will start at 6:30pm NZT.
Why watch: No one has ever managed to break the sub-2h barrier for the marathon. Kipchoge has come closer than anyone and is, for all intents and purposes, the most qualified human to break this barrier. Many people believe it simply cannot be done. If he does it today, you will be witnessing history being made.
Can it be done?
Let's put it this way: if anyone can do it, it's probably Kipchoge.
In fact, no one has ever come as close as he has and he's done pretty much everything else there is to do in the world of athletics — except that.
The run in Vienna sounds like the perfect ground to break this barrier. Kipchoge will be running 9.6km paved circuits in a park called The Prater. The park is well shaded and the circuits will be flat, with spectators lining the course. Back in Monza in 2017, Nike's event was closed to the public. The crowd cheering for the Kenyan runner in Vienna could be just the extra incentive he needs to run those 26 seconds faster.
Prater Park was chosen in a worldwide hunt for the perfect spot for this attempt, using software that analysed factors such as temperature, humidity, wind speed, elevation and other criteria.
Failing that, he also has some of the world's fastest runners as a crew of pacers. His rotating pacer team includes names such as Bernard Lagat, Lopez Lomong, Matthew Centrowitz, Paul Chelimo, and Norwegian siblings Henrik, Filip, and Jakob Ingebrigtsen.
The 34-year-old runner also has the best CV of any distance runner, with Olympic gold medals, numerous world titles and the world record under his belt. The sub-2h marathon truly is the only thing left for him to achieve.
In a video for the INEOS 1:59 Challenge documentary series, Kipchoge says he is doing it "to make history".
"Many ideologies [have] been going that no human will break the two-hour mark but personally, I have dared to try," he says.
At 7.15pm NZT tonight, Kipchoge will start running on Vienna's Reichsbrücke Bridge. He will run 1.2km to the Praterstern roundabout. The round around it has been resurfaced to maximise his efficiency on it.
His run to the park has an elevation drop of 16 metres, making it technically a downhill. Once in the park, he will run four laps of a 9.6km circuit, followed by a final stretch to make up the exact marathon distance.
The course inside the park is almost completely flat, with a total of 2.4m of elevation change.
Pacers will take terms running alongside Kipchoge in a specific formation designed to maximise his efficiency.
Five athletes will run in front of him in a V-shape, and two runners will go just behind him to either side, to reduce drag.
A car will be driven in front of the runners at a pace of 2:50 per kilometre, and runners will follow a line projected on the road.
Kipchoge will be handed drinks from a bicycle rather than from a table.
He will drink a special carbohydrate drink. Every time he takes a drink and discards the bottle, it will be picked up and weighed to quantify exactly how much he consumed.
He will be running in Nike shoes to be released next year, a newer version of the shoes in which he has previously broken records.
