Aidan P. O'Brien

Birthdate: October 16, 1969

Birthplace: County Wexford, Ireland

Residence(s): Ballydoyle, Cashel, County Tipperary, Ireland

Family: Wife, Anne-Marie; children, Joseph (a former jockey now training), Sarah, Anna and Dennis

Aidan O’Brien was the son of a farmer and small-time trainer who apprenticed with Jim Bolger for three years before taking over the racing license of his wife, champion jumps trainer Anne-Marie, daughter of trainer Jim Crowley, in 1993. O’Brien secured champion amateur riding honors over the jumps the following year at age 23, and went on to champion jumps trainer for five years while also training on the flat. He shifted to training only flat horses after the retirement of his top jumper Istabraq in 2000.

Backed by the Coolmore operation, O’Brien has rewritten the record books since he became the youngest champion trainer in 1996, his second year headquartered at storied Ballydoyle in County Tipperary. His many training championships since — deserved for the multiple wins in each of the classics in Europe, multiple Breeders’ Cup victories, and successes in other top races in Europe and North America — have been earned by his rarely relaxing his famous focus. O’Brien leaves his Ballydoyle operation as close to a race as possible and returns right afterward. However, he has enjoyed taking his kids to Disneyland following Breeders’ Cups at Santa Anita Park.  

O'Brien won his second straight U.A.E. Derby with Lines of Battle in 2013, cementing both horse and trainer a spot in the Kentucky Derby. O'Brien has started four horses in the Derby with his best finish coming from Master of Hounds, who finished fifth in the race.

O'Brien has won numerous Breeders' Cup races in his career including a score in the Breeders' Cup Turf with Highland Reel in 2016, which was his sixth win in the race, and then a win in the 2017 Juvenile Turf with Mendelssohn. After a drought of three years, O’Brien picked up his 13^th Breeders’ Cup win in 2020 when also-eligible longshot Order of Australia won the FanDuel Mile Presented by PDJF. That was his first win in the Mile.

O'Brien was back on top again at the 2022 Breeders' Cup at Keeneland, where he won twice on "Future Stars Friday." His 2-year-olds won both the Breeders' Cup Juvenile Fillies Turf and the Juvenile Turf. O'Brien's favored Meditate accelerated to an impressive 2 1/2-length victory in the Juvenile Fillies Turf, and later his Victoria Road won a stretch duel by a nose in the Juvenile Turf to cap-off his two-win day. On the Saturday of the 2022 Breeders' Cup program, O'Brien added another winner when his 3-year-old filly Tuesday scored in the Maker's Mark Breeders' Cup Filly & Mare Turf. 

In 2023 at Santa Anita Park, O’Brien added to his Breeders’ Cup resume with victories 17 and 18. O’Brien’s Unquestionable won the Prevagen Juvenile Turf by 1 ½ lengths as the 3-2 favorite and the next day Auguste Rodin struck by three-quarters of a length in the Longines Turf.

Lake Victoria got O’Brien off to a fast start at the 2024 Breeders’ Cup at Del Mar when she won the John Deere Juvenile Fillies Turf as the odds-on favorite for her fifth win in as many starts. Two races later on the Nov. 1 Future Stars Friday card, the trainer added another 2024 Breeders’ Cup win with late-running Henri Matisse in the Juvenile Turf.

Those two wins in 2024 put O’Brien in a tie for first among all trainers with 20 victories at the Breeders’ Cup, joining D. Wayne Lukas. The 2025 event marked the first Breeders’ Cup without Hall of Famer Lukas, who died in June, and on Oct. 31 in the final Future Stars Friday race, O’Brien scored career Breeders’ Cup victory number 21 when Gstaad rallied to take the Juvenile Turf.