The World Eventing Championship for Young Horses in Le Lion, France was abandoned on Friday because of poor weather.
Heavy rain left parts of the cross-country course under water, giving organisers little option but to abandon the six and seven-year-old classes after dressage.
British riders Kitty King, Laura Collett and Oliver Townend were among those firmly in contention before the weather intervened.
In a statement on the event's website, organisers said: "Because of exceptional weather conditions, and after considering all alternatives to preserve the safety of horses, riders and the public, no satisfactory solution has been found.
"As a result, the organisers, in agreement with officials of the International Equestrian Federation are sorry to announce the cancellation of the 27th Mondial du Lion."