Aidan O’Brien is Ireland’s most successful racehorse trainer and one of the greatest of all-time anywhere. He is one of the sport’s most recognisable figures, and even in middle-age he retains much of the boyish, bespectacled look he had when he burst on to the scene in the mid-1990s.

O’Brien trains out of the famous Ballydoyle Stables in Ireland, having taken over from another legend of world horseracing, Vincent O’Brien, to whom he is no relation. Like his namesake, O’Brien’s prodigious success is entwined with John Magnier and the mighty Coolmore breeding empire.

He has been Ireland’s champion trainer every year since 1999 and has been champion trainer in Britain six times, having trained the winner of the Derby at Epsom a record 10 times.

Horse trainer Aidan O'Brien and jockey Ryan Moore

Aidan O’Brien’s father Denis O’Brien was a farmer who trained a few race horses in rural County Wexford. O’Brien was an amateur jockey over jumps and worked for trainer P J Flynn before moving on to Jim Bolger’s Group 1 operation where he impressed his boss.

Having married Anne-Marie Crowley, he took over from his wife (Ireland’s champion National Hunt trainer in 1992-93) as the licence holder at her family’s Piltown stables in June 1993 and has never looked back. He was champion National Hunt trainer for the first time at the age of 24, and held that title for five consecutive seasons (1993-94 to 1997-98), during which time, in 1996, he moved to Ballydoyle and joined the Coolmore fold.

His first Group 1 win came that year when the subsequent Irish 2,000 Guineas and Irish Derby winner Desert King won the National Stakes. The following spring Classic Park gave O’Brien his first classic win in the Irish 1,000 Guineas. He notched his 100th European classic success when Auguste Rodin won the 2023 Irish Derby.

Horse trainer Aidan O'Brien and jockey Mick Kinane

O’Brien has the luxury of having a stable choc-a-bloc with some of the finest horseflesh in the world, which does help matters considerably. But he is in that position in the first place because he is a gifted horseman renowned for his remarkable attention to detail. He knows his horses individually, their characters and their needs, and prepares them accordingly. There is no set pattern: he is just as expert at preparing a sharp early two-year-old sprinter as he is at patiently developing a slow-maturing stayer. He puts great stock in the team aspect of his stable and staff.

Horse trainer Aidan O'Brien and jockey Jamie Spencer

Many in Britain and Ireland would place Istabraq at the head of any list of O’Brien-trained champions. The gelding won the Champion Hurdle at Cheltenham three times and is an icon of the National Hunt game with 13 Grade 1 wins in total. But, in terms of flat racing, with its global scope, Galileo is the pick.

O’Brien trained the son of Sadler’s Wells to win his first six races, including impressive victories in the Derby, Irish Derby, and King George VI & Queen Elizabeth Stakes. He was second in an epic tussle with Godolphin’s Fantastic Light in the Irish Champion Stakes, thwarted by Frankie Dettori at his best, and can be forgiven his final run when sixth on the Belmont dirt in the Breeders’ Cup Classic.

Galileo was a brilliant racehorse, but perhaps it could be argued he was no better on his day than other O’Brien stars like ‘the Iron Horse’ Giant’s Causeway or High Chaparral or Dylan Thomas. But what sets Galileo’s profile higher than all is his exceptional qualities as a champion stallion of rare dominance, a breed shaper that provided Coolmore and O’Brien with Group 1 winner after Group 1 winner for the best part of two decades.

Aidan O'Brien's Epsom Derby winner Galileo

His achievements are numerous – including a record-equalling 20 Breeders’ Cup wins – and will place him in history as one of the sport’s all-time greats, but winning a record 28 Group 1 races in 2017 was a mighty feat. That haul bettered the 25 Group/Grade 1 wins by the late Californian trainer Bobby Frankel and was achieved with 14 different horses.

Aidan O’Brien and his son Joseph made history as the first father and son, trainer and jockey, combination to win the Derby at Epsom when Camelot triumphed in 2012. They repeated the feat for good measure in 2014 with Australia in the Cox Plate.

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