In 2020, he set the record for the number of Epsom Derby winners sired at five: New Approach, Ruler Of The World, Australia, Anthony Van Dyck and Serpentine.
Galileo was euthanized on 10 July 2021, after a debilitating injury to his near foreleg which failed to heal after surgery earlier that year.
His breeders were David Tsui, the owner of Urban Sea, and "Orpendale", a name used by the Coolmore Stud organisation for some of their breeding interests.
Owned by Sue Magnier and Michael Tabor, Galileo was sent into training with Aidan O'Brien, then just starting his tenure at Ballydoyle.
Noel Stapleton, his long-time handler at Coolmore Stud, called him a creature of habit: "He is a true gentleman, and I think he knows how important he is.
The most notable "other" Galileo was a Polish-bred gelding which won the Grade I RSA Novices' Hurdle at the 2002 Cheltenham Festival.
He was made the even-money favourite, despite the field containing two runners each from the stables of the leading Irish trainers John Oxx and Jim Bolger.
[12] On his debut, he was 1/3 favourite for the Listed Ballysax Stakes over a mile and a quarter at Leopardstown, which he won "easily" by three and a half lengths.
The odds-on favourite, he was ridden for the first and only time by Seamie Heffernan, as Kinane was riding Milan in the Group One Prix Lupin on the same day.
[17] Following the race, Timeform assigned a figure of 130 to Galileo, making him, in their opinion, the best Derby winner for ten years.
[20] Kinane, who was winning his first Irish Derby in seventeen attempts, said that he was always in "complete control", while Morshdi's jockey, Philip Robinson, described the winner as "a freak".
[21] Galileo was then tested against older horses in the King George VI and Queen Elizabeth Diamond Stakes at Ascot in July.
The betting suggested a match between Galileo (1/2 favourite) and the Godolphin five-year-old Fantastic Light (7-2), who had won Group One races in four different countries.
[22] Galileo returned to Leopardstown in September for a much-anticipated[23] Irish Champion Stakes against Fantastic Light again, this time over the shorter distance of one and a quarter miles.
The plan failed, as the rest of the riders ignored Ice Dancer, who went ten lengths clear before stopping abruptly in the straight.
In the 2001 International Classification (the forerunner of the World Thoroughbred Racehorse Rankings), Galileo was assessed at 129 (equal with Fantastic Light), making him the third highest rated horse behind Sakhee and Point Given.
He originally operated as a "shuttle" stallion, standing at Coolmore's main farm at Fethard, County Tipperary Ireland during the Northern Hemisphere breeding season and moving to its Australian branch in the Hunter Valley, New South Wales for the Southern Hemisphere breeding season.
This tied him with Cyllene, Waxy, Sir Peter Teazle, Blandford and Montjeu for the number of Derby winners sired.
[8] In the 2019 Derby, he was the sire, grandsire or great-grandsire of all runners but Sir Dragonet, who was related to Urban Sea through his full sister All Too Beautiful.
When announcing the death, John Magnier of Coolmore commented, ""The effect he is having on the breed through his sons and daughters will be a lasting legacy, and his phenomenal success really is unprecedented.
"[44] c = colt, f = filly, g = gelding Breeders' Cup Turf, Coronation Cup, Prince of Wales's Stakes † Noble Mission was awarded the Grand Prix de Saint-Cloud, after another Galileo son called Spiritjim was demoted from first after it was found that he tested positive for banned substances.
[45] ‡ Gleneagles was demoted from first to third in the 2014 Prix Jean-Luc Lagardère, after stewards deemed him to have interfered with the horse that finished second (Full Mast) and third (Territories).