Olympic medallist Bettina Hoy and European champion Nicolas Touzaint are the latest riders to sign up for Express Eventing.
Swedish star Linda Algotsson and American Buck Davidson are also named among the creme de la creme of equestrian riders who will be competing for the Express Eventing International Cup at the Millennium Stadium on 30 November.
Sixteen other world class riders have already signed up - British Olympians Mary King, Tina Cook and William Fox-Pitt, British riders Lucy Wiegersma and Oliver Townend, New Zealand Olympians Mark Todd, Andrew Nicholson and Caroline Powell, German Dirk Schrade, Belgian Karin Donckers, Italian Vittoria Panizzon, American Philip Dutton, Australians Clayton and Lucinda Fredericks, Chinese teenager Alex Hua Tian and Rodolphe Scherer from France.
Express Eventing, in association with British Eventing, will combine all the skill and excitement of three day eventing in just half a day, within the enclosed sporting arena of the Millennium Stadium.
This new competition is designed to open up the sport to a wider global audience and provide a showcase for eventing's top riders. For the very first time, spectators will be able to watch all three disciplines - dressage, show jumping and cross-country from one seat, and follow the progress of every horse and rider at each stage of the competition.
Former international rider and the brains behind the concept, Stuart Buntine, said: "Express Eventing is designed to promote traditional eventing, not to replace it. Three day events are held in fabulous places, but they actually last over five days and the competitions are spread out, making it difficult for the public to follow what's going on. With Express Eventing, spectators can watch all three phases without moving from their seat.
Riders will be competing for an unprecedented a £100,000 first prize, part of a £250,000 prize pot.