London Marathon organizers have announced a one-off expansion of the London Marathon into a two-day event for 2027, taking place April 24-25. The format doubles the field to 100,000 participants on the same course that runs from Greenwich to Westminster. It will be the largest marathon event across two days.

What you need to know:

– A record 1.33 million people entered the ballot for the 2027 event.

– Elite women, female para-athletes, and women's championship/good-for-age runners lead one day's mass event. Elite men, male para-athletes, and men's championship/good-for-age runners will run the other.

– Everyone already in the ballot is entered into a draw for both Saturday and Sunday.

– No participant can run both days in-person, but can combine one in-person day with the virtual TCS London Marathon MyWay on the other.

– Ballot results announced early July via random draw.

What they had to say:

Hugh Brasher, CEO of London Marathon Events: “The 2027 TCS 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. 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.”

Mayor of London, Sadiq Khan: “London is the sporting capital of the world and I am delighted that, for one year only in 2027, the world famous TCS London Marathon will expand into a two-day event. “This unique, one-off double will allow a record 100,000 participants to take part across the two days - creating the largest fundraising moment in UK sporting history and supporting the work of so many incredible charities. The London Marathon showcases the very best of our capital and we will continue working closely with London Marathon Events and our partners to ensure appropriate measures are in place for the entire weekend as we build a better, more prosperous London for everyone.”

How it compares to other races:

– The 2026 London Marathon broke the world record for biggest marathon with 59,830 finishers. The previous best was 59,226 set by the TCS New York City Marathon in November 2025.

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