Two-time Olympic champion Lord Coe and comedian John Bishop will go head to head next month as part of this year's Sport Relief.
Coe and Bishop will lead two teams of celebrities in sporting challenges at London's Queen Elizabeth Olympic Park.
Events, including rhythmic gymnastics, track cycling and swimming, will be broadcast live on the BBC on 21 March.
Bishop, 47, said: "Am I intimidated by going up against Sebastian Coe? No, bring it on!"
Coe won gold in the 1500m, and silver in the 800m, at both the 1980 and 1984 Olympics.
He later led London's successful bid for the 2012 Olympics and was subsequently made chairman of Games organiser Locog.
The 57-year-old said: "I spent the best part of 10 years preoccupied with the planning and delivery of London 2012.
"Not once did I imagine that less than two years later I would find myself back at the park competing.
"I hear John Bishop has quite a competitive streak but I know these venues inside out - something that, probably unrealistically, I am hoping will play to my advantage."
In 2012, Bishop completed a five-day challenge to cycle, row and run the 290 miles from Paris to London in aid of Sport Relief, a feat he described as "the biggest physical challenge of my life".
The 2014 Sport Relief Weekend takes place from 21-23 March and money raised will help some of the poorest and most disadvantaged people in the UK and around the world.
Last week, TV presenter Davina McCall completed a 500-mile triathlon challenge from Edinburgh to London, raising more than £760,000.