One of the biggest operations in British and Irish horse racing will be phased out over the next five years.
Michael O'Leary, who owns the team of horses in Gigginstown House Stud in Ireland that includes reigning two-time Grand National winner Tiger Roll, made the shock announcement on Tuesday.
"As my children are growing into teenagers, I am spending more and more of my time at their activities and I have less and less time for National Hunt racing, a situation that will continue for the foreseeable future," said O'Leary, a charismatic figure who is best known for being the chief executive of budget airline Ryanair.
"I hope that by running down our string over an extended four or five-year period it will give our trainers ample time to replace our horses without disruption."
The Gigginstown team, which first owned flat-racing horses before becoming involved in jumps racing, has more than 250 horses in training in Ireland and had 922 runners in the most recent Irish campaign. It was the champion owner in Ireland for the seventh time when the season ended at Punchestown this month.
Gordon Elliott, who looks after Tiger Roll, and Joseph O'Brien are two of the top trainers of O'Leary's horses.
Another Grand National winner, Rule The World (2016), and Cheltenham Gold Cup winners War Of Attrition and Don Cossack were also part of the 58-year-old O'Leary's operation, which has had 27 winners at the Cheltenham Festival.
O'Leary said he will not be buying any more horses, leaving a gap in the market for another racehorse owner to become the dominant force in Ireland.
"We have lots of young stock to be allocated among our trainers over the coming weeks," said O'Leary's brother, Eddie, who has long acted as racing manager for Gigginstown.