Worlds Toughest Ultramarathons
There are many events that claim the title of Toughest Race in the World and it becomes clear that each event makes that claim based on unique features of the event. This then is a list of ultramarathons who have a reasonable claim to the title, in no particular order.
Other serious endurance races
- Iditarod Invitational (Mushing)
- Race Across America (Cycling)