Champion jockey AP McCoy and Olympic eventer Zara Phillips are to face each other at the Barbury Horse Trials.
The duo head the line-up for a race between jump jockeys and event riders to be held on 5 July.
McCoy will compete with ex-champion jockey John Francome and Sam Twiston-Davies, stable jockey to Paul Nicholls.
Phillips is joined by world number one William Fox-Pitt, two-time Olympic gold medallist Sir Mark Todd and 2009 Young Rider European champion Laura Collett.
Showjumpers competing at the event in Wiltshire will make up a third team, and the winners from the Inter Hunt Scurry, held on the same day, will form the fourth team.
The event will be held as a relay race on specially designed course, including a water jump in Barbury's main arena.
"They'll jump jumps and hand over a baton, as well as going over the water," said Barbury chairman Nigel Bunter.
"We came up with the idea of a fast-run race between iconic riders. We've got the best in the world at eventing and racing and we hope to announce some of the best showjumpers as well."
Seven-time National Hunt champion Francome added: "It will be a challenge but the one thing we know about AP is that he's ultra-competitive.
Barbury Horse Trials will celebrate its 10th anniversary this year, and the Injured Jockeys' Fund will be the event's official charity.