Irishman Joseph O'Brien has become the youngest jockey to win a Breeders' Cup race by triumphing on St Nicholas Abbey - trained by his father Aidan.
The 18-year-old beat Britain's Sea Moon to win the $3m (£2m) Breeders' Cup Turf race at Churchill Downs, Kentucky.
Settled in mid-division, the Montjeu colt picked up superbly when angled out for a run.
An emotional O'Brien senior paid tribute to his son, saying: "It's been one of the proudest days of my life."
He added: "It's unbelievable, a wonderful ride. What can I say? He's an incredible rider."
BREEDERS' CUP EXPLAINED
- The Breeders' Cup is an annual series of thoroughbred horse races, which is being held over two days this year. Since the inaugural running at Hollywood Park 27 years ago, it has become the season-ending championship of thoroughbred racing
St Nicholas Abbey had taken the lead in the stretch and hit the wire two and a quarter lengths ahead of Sea Moon.
Joseph O'Brien said: "It's a dream come true. I've been coming to the Breeders' Cup since I was very small, but to ride here and ride a winner - it's out of this world."
The victory gave the trainer and St Nicholas Abbey's owners, the Irish-based Coolmore racing empire, a big race double after the success of Wrote in the BC Juvenile Turf race.
Coolmore partner Derrick Smith added: "This is a day from the Gods."
During 2011, Joseph O'Brien has become one of the most accomplished young riders in Ireland and Britain, being entrusted by 'outside' trainers as well as his father.
However, standing at 5ft 11ins, he is tall for a jockey and acknowledges with weight an issue, his riding days are possibly numbered.
He said: "I'll go on for as long I can, but I'm not going to kill myself [to achieve low weights]."
There has been talk of O'Brien, who landed his first Classic race in May when Roderic O'Connor took the Irish 2000 Guineas, embracing jump racing where the weight scale is less demanding.
But while that remains a possibility, there is also believed to be a chance that he will eventually become part of the Coolmore training team.
The Sir Michael Stoute-trained Sea Moon, only racing for the sixth time and surely one to follow in 2012, had looked likely to take the prize before O'Brien brought St Nicholas Abbey with the winning run.
Brilliant Speed ran a cracker in third, while the French filly Sarafina was a luckless 4th having moved well through the race.
The winning jockey said: "The horse was always going easy, and picked up when it mattered. I had to be patient and wait for the gaps but when I got out at the bottom of the straight, he picked up really well.
"It's a dream come true. I've been coming to the Breeders' Cup since I was a little boy, and this is out of this world."
The success of Wrote as well as St Nicholas Abbey took Aidan O'Brien's Breeders Cup tally to six over the years, but big hope So You Think finished just out of the frame behind Drosselmeyer in the $5m Classic race.