Deepest marathon
- Who
- BecomingX, ICMM, Boliden
- What
- 1,118.56 metre(s)
- Where
- Sweden (Garpenberg)
- When
- 25 October 2025
The deepest marathon is 1,118.56 m (3,669 ft 10 in) and was achieved by BecomingX (United Kingdom), ICMM (United Kingdom) and Boliden (Sweden) in Garpenberg, Sweden, on 25 October 2025.
55 runners from 18 countries took part in the World’s Deepest Marathon inside Boliden’s Garpenberg zinc mine in Sweden. The event was held on a certified 42.195-km course at an average depth of 1,100.43 m below sea level. The attempt covered two Guinness World Records titles: Deepest Marathon (individual) and Deepest Underground Marathon Distance Run (team). Participants completed 11 laps of the designated underground route and collectively raised up to $1 million for charity.