The London Marathon will be split across two days in 2027 as a special one-off event.
More than 1.33 million people entered the ballot for next year's race, prompting organisers to announce that they were exploring ways that would allow for more participants.
A change to a two-day event -- taking place on Saturday 24th May and Sunday 25th May -- will effectively double the chances of success in the ballot and allow for 100,000 people to take part.
Ballot hopefuls will know their fate in early July and will be receive ballot entries for both the Saturday and Sunday.
As well as the increased participation, the change is also expected to raise more than £150m for various charities, as well as providing a £400m benefit to the UK economy.
"The 2027 London Marathon double is our most ambitious evolution to date - a once-in-a-generation one-time-only reimagining of what a marathon and city-wide celebration of activity can be," said Hugh Brasher, chief executive of London Marathon Events.
"By expanding to 100,000 runners across two days, we're opening the door for more people, more charities and more communities to take part in the world's greatest marathon. We believe that more than £150m can be raised for good causes and the UK economy will have a £400m social and economic benefit.
"We are grateful for the vision and support of the Mayor of London, the councils on the route, the emergency services, and all the stakeholders involved who have given their support to enable this world first event to be held for London and the UK."
There were a record 59,830 finishers in the 2026 event and it was the single biggest annual one-day worldwide fundraising event, with over £90m raised for various causes.
History was also made on the track when Kenyan athlete Sabastian Sawe became the first man to run a sub two-hour marathon in a competitive race.
The initial plans for 2027 is for the elite women, elite female wheelchair athletes, championship and 'good for age' women to lead Saturday's mass event with the elite man, elite male wheelchair athletes, championship and 'good for age' men to kick the day off on the Sunday.
