Harbinger is to leave the UK for Japan after being bought by the Shadai Group for stud duties.
The four-year-old was officially the highest-rated racehorse in the world prior to suffering a career-ending injury during the summer.
His last appearance brought an 11-length victory in the King George VI And Queen Elizabeth Stakes at Ascot in July - Harbinger subsequently sustaining a fractured a leg on the Newmarket gallops.
Owners Highclere Thoroughbred Racing have since been considering number of possible stud destinations but the Shadai Group have won through.
Highclere director John Warren said: "There were a number of top stud farms from both home and abroad involved in the negotiations and there was a very strong bid to keep the horse in England.
"Unfortunately for the British bloodstock industry the final bid from the famous Shadai Group, where Sunday Silence stood, was far too strong to be able to compete.
"The owners of Highclere Thoroughbred Racing's Admiral Rous syndicate grew extremely close to the horse.
"They would dearly have loved Harbinger, widely regarded as 'the best horse in the world', to have retired to stud in the UK.
"However, he will be in excellent hands and we hope he is as big a success at stud for the Yoshida brothers as he was on the racecourse for us.
"It has been a privilege to have been involved with such a great horse.
"Harbinger is recovering well and is a model patient. He should be sound enough to travel within a few months. The required tests for export are ongoing but at an advanced stage."
Trained by Sir Michael Stoute, Harbinger won six of his nine career outings, earning prize money in excess of £750,000.
Connections said the multi-million dollar deal values the horse as one of the highest-priced transactions in recent times.
