List of leading Thoroughbred racehorses

This list of leading Thoroughbred racehorses contains the names of undefeated racehorses and other horses that had an outstanding race record in specific categories. Note though that many champions do not appear on the list as an unexpected defeat may be caused by many factors such as injury, illness, going, racing tactics and differences in weight carried, the latter being particularly significant in North America and Australia where handicaps are common even at the highest level of racing.
It is common to compare racehorses on multiple factors such as their overall race record, the quality of the horses they beat and the brilliance of their wins. Comparison of raw times is generally unreliable between horses of different eras or even over different racecourses due to a variety of factors such as the racing surface and the pace at which the race is run. Timeform ratings, introduced in 1948, and Beyer Speed Figures, introduced in the United States in 1992, are relatively recent attempts to compensate for such variables. Thoroughbred Winning Brew holds the Guinness world record for the fastest speed from the starting gate for a Thoroughbred racehorse, at 70.76 km/h (43.97 mph) over two furlongs, although Quarter Horses attain higher speeds over shorter distances than Thoroughbreds. Such speeds may also be achieved by elite racehorses during the stretch drive.
The two main forms of Thoroughbred horseracing are flat racing and hurdle or steeplechase (jumping) races over obstacles. Jumpers tend to be older than their flat racing counterparts and can have much longer careers, making it possible to earn a large number of wins. For example, champion hurdler Hurricane Fly won a then-record 22 Grade One races over his ten-year career.
Most race horses and race winners are male horses (either intact males or geldings). While male and female horses do not exhibit sexual dimorphism as obviously as human athletes, male horses are considered more aggressive racers and generally have a significant competitive advantage. At the highest level of racing though, intact males have great economic value at stud, so they are often retired after only a few years of racing. In part because they may have longer racing careers, some of the most winning racehorses of all time are females, including Kincsem, Black Caviar, Winx, and Zenyatta.
Below is a list of Thoroughbred racehorses with an undefeated race record. The list is not comprehensive for otherwise unnotable horses with five or fewer starts.
*Although Justify finished first in all his races, in 2024 he was officially disqualified from his win in the 2018 Santa Anita Derby, making his official record no longer undefeated. A pending appeal contesting this disqualification was filed in April 2024.
Federico Tesio bred several undefeated champions including Nearco, Ribot, Braque, and Cavaliere d'Arpino, whom he considered the best horse that he ever bred.
Nordlicht (chestnut horse 1941–1968, by Oleander x Nereide, by Laland) was also undefeated after an unknown number of starts. His victories included the Deutsches Derby and Austrian Derby. Middleton and Amato had one start each with both of them winning The Derby and then retiring. Cherimoya did likewise when she won The Oaks in her only start. Morston (colt by Ragusa x Windmill Girl by Hornbeam) had two starts, winning both, the second of which was the 1973 Epsom Derby. Sailor won both his races, including the 1820 Epsom Derby. Suspender had three starts, in smaller races, for three wins. Don Juan by Loyalist, Ball's Florizel (1801), Mirza by the Godolphin Arabian, and Lecturer (1869), were also unbeaten, but the number of their wins is unknown.
There have been only 7 horses to win over 100 races, all of them coming from Puerto Rico in restricted racing. The all-time record, recognized by Guinness World Records, is held by Chorisbar who won 197 times over the course of 324 career starts. Condado, a chestnut horse who raced in Puerto Rico from 1936 to 1943, won a grand total of 152 times Galgo Jr. earned 137 wins in 159 starts from 1930 to 1936. Cofresi won 119 races, racing at around the same time as Condado.
In the United States, Kingston (by Spendthrift) had 138 starts and won 89 of these, including 30 stakes-races. According to the American Horse Racing Hall of Fame, his 89 wins set the all-time record. Commencing a winning sequence as a four-year-old on 21 August 1888, Kingston had 35 race starts until 30 May 1891 during which he was defeated only twice. Bankrupt won 86 races from 348 starts, and he was also by Spendthrift. Tippety Witchet (1915, by Broomstick) started 266 times for 78 wins. Pan Zareta started 151 times with 76 wins and is considered to be the "winningest female Thoroughbred in American history".
Catherina (1830, by Whisker) started in 176 races and won 79 of them, many over long distances, including the Manchester Cup, Tradesmen's Cup, and Heaton Park's King's Cup. Many of Catherina's races were heat races, and she therefore actually faced the starter 298 times and was the first past the finish line 136 times, including two disqualifications, one walkover, and two dead-heats.
The horses who were defeated but had ten or more consecutive race wins include
‡ Filly or mare
*The ninth race in Kelso's streak was earned via disqualification.
Horses with long sequences of jumping victories include Sir Ken, who won 16 hurdle races in England; and Poethlyn, who won 11 steeplechases in succession, including two Grand National races.
To identify the highest quality races, the pattern race system was introduced in Europe in 1971, followed by the graded stakes system in North America in 1974. Other countries followed suit, though the criteria and quality has not always been consistent between racing jurisdictions. The following list considers horses that won grade one / group one races that were open for International competition. Winners of local (restricted) group / grade one wins are not included.
The horses with ten or more such G1 race wins are:
‡ Mare
In 1902 Sceptre became the only racehorse to win four British Classic Races outright. Previously, in 1868, Formosa won the same four races but dead-heated in the 2,000 Guineas Stakes.
This list shows horses who won a series of Grade/Group 1 races without a loss and without an intervening race at a lower level of competition.
‡ Mare
‡ = Filly or mare
Below is a list of Thoroughbred racehorses who were defeated once. The list is not comprehensive for otherwise unnotable horses with fewer than ten wins.
Horses such as Wheel of Fortune, Barbaro, Ruffian and Vanity (1812, either 10:9-0-0 or 12:11-0-0) sustained injury or broke down in their only defeat.
*The disqualification of Justify in the 2018 Santa Anita Derby is currently under appeal.
The following horses have earned over $10 million in prize money. Most of them raced (at least in part) in Japan, Hong Kong, Australia and/or Dubai due to large purse sizes. Where applicable, the conversion to US$ was made at the time the horse raced so does not reflect current exchange rates. Different methodologies for currency conversions may result in slightly different rankings. This list may not reflect recent results
*Horses still in training
**Value calculated using exchange rates rather than an official earnings record, generally for the last year the horse raced
Most of the above horses belong to the Nearco sireline, mostly through the branches established by Sunday Silence and Northern Dancer. However, Curlin, Arrogate, Winx, Hokko Tarumae, Panthalassa, and Gun Runner descend instead from the Native Dancer sire line through Mr. Prospector. Both Nearco and Native Dancer were grandsons of Phalaris.
rMiss Woodford was the first to earn over $100,000, in 1885. In 1951, Citation became the first horse to win one million dollars. In 1979, Affirmed became the first horse to break the two million dollar barrier, finishing his career with earnings of $2.3 million. Purses began to increase sharply soon afterwards thanks in large part to the Breeders' Cup. John Henry was the first to surpass $5 million, earning just shy of $6.6 million by the end of his career in 1984. Curlin in 2008 became the first to earn $10 million. California Chrome broke this record in 2016 with career earnings of $14.8 million, and was in turn surpassed by Arrogate when he won the 2017 Dubai World Cup to take his career earnings over $17 million.
The overall progression of the leading North American is as follows (year is when the record was broke, although earnings reflect lifetime earnings):