What’s in a Name: A Look at the Rules for Naming Thoroughbreds

Apr 25, 2025 Jennifer Kelly / TwinSpires.com

Eighteen characters is all an owner gets when naming their equine athlete and perhaps establishing a moniker that evokes a legacy akin to that of Man o’ War or Secretariat. Those eighteen characters include both spaces and punctuation and do not come with a guarantee of success, either that you will get the name you apply for or that your horse will win a race. However, naming your next star does present a fun challenge.

The Jockey Club, which maintains the American Stud Book and with whom each Thoroughbred must be registered prior to their first start, does have a few rules for the naming process.

Names cannot consist of only initials or be comprised entirely of numbers. The 2023 Champion Two-Year-Old Filly Just F Y I is an amalgam of her sire Justify’s name and stays within the rules, while Thirty Six Red, who finished ninth behind Unbridled in the 1990 Kentucky Derby, ably handles the rule about numbers.

Owners cannot use the names of living persons unless written permission to do so is submitted to the Jockey Club. When owner Carl Rosen wanted to name his filly by Swoon’s Son after tennis star Chris Evert, he sought permission from the Grand Slam champion to submit her name for his own future champion. She granted him permission, and the equine Chris Evert went on to win the Triple Tiara – the Acorn (G1), the Mother Goose (G2), and the Coaching Club American Oaks (G1) – and then became a Hall of Famer on the strength of her winning career.

Owners cannot reuse the names on the Jockey Club’s Permanent list. This includes horses in racing's Hall of Fame; horses who have won an Eclipse or a Sovereign Award; cumulative money winners of $2 million or more; horses who have won one of the Triple Crown classics, the Jockey Club Gold Cup (G1), the Breeders' Cup Classic (G1), or the Breeders' Cup Turf (G1); and horses included in the International List of Protected Names. The 2025 Road to the Kentucky Derby contender Omaha Omaha, a colt by Audible, could not be simply Omaha, our third Triple Crown winner, so owners On Your Left Racing had to call an audible (ha!) and go for Omaha Omaha instead.

Owners cannot reuse the names of horses by the same sire or out of the same dam as the foal or names of horses appearing within the first five generations of a foal’s pedigree. If you have a foal by out of the mare Puca, that owner cannot reuse the previous names of her foals, like Kentucky Derby winner Mage, Belmont Stakes (G1) winner Dornoch, or her current possible Derby contender Baeza. Also, a foal with the late Leslie’s Lady in its pedigree could not have that name either if she appeared within the first five generations.

Owners must avoid names that are currently active either in racing or breeding. The name of any horse actively participating in the sport, either on the track or in the breeding shed. An exception comes if the horse in question is over 10 years old and is not currently active in either breeding or racing. The Jockey Club shares a list of recently released names to simplify the task.

Owners cannot register the names of winners of grade one stakes races over the last 25 years. Whitmore retired from racing in 2021 after seven seasons on the racetracks with two Grade 1 wins to his name, the 2018 Forego (G1) and the 2020 Breeders’ Cup Sprint (G1). If an owner wanted to use that name for their own burgeoning equine athlete, they would have to wait until 2045, a quarter-century after his Breeders’ Cup victory.

The list of rules for naming a Thoroughbred also say that a horse’s name cannot end in terms like “filly,” “colt,” “stud,” “mare,” “stallion,” or any similar horse-related term; include a numerical designation such as “2nd” or “3rd,” whether or not such a designation is spelled out; use the name of racetracks or graded stakes races; or use the names of persons no longer living unless The Jockey Club grants approval. Additionally, the registrar can reject names at their discretion, including any that might include a profane or obscene meaning, are likely to be offensive, or could be inflammatory or controversial, especially if they are insulting or demeaning to the sport.

A foal must be registered with the Jockey Club within 12 months of birth, but does not require a name until Feb. 1 of their two-year-old season. The owner must pay a fee to claim a name if no racing name is registered by that date. When registering their newest athlete, an owner can submit multiple names for one horse; the 1970 colt by Bold Ruler out of Somethingroyal had six names submitted and rejected until Meadow Stables submitted Secretariat, which, of course, was approved. Once an owner registers their new racehorse, they can change their name up until they make their first start. After that, if a horse must be renamed, they run with both names in the program until they have started three times under their new name.

Have a list of names for future racehorses? The Jockey Club has a searchable online book of names that you can use to see if those names are currently taken.

The Jockey Club's naming rules are a fascinating intersection of tradition and practicality, ensuring the uniqueness of each equine athlete's identity. While sometimes leading to unusual names, these conventions help maintain clear records for future generations. These guidelines play a crucial role in preserving the integrity and distinctiveness of the Thoroughbred while also giving us fun names like Fluffy Socks, Gas Station Sushi, and the unforgettable Notacatbutallama.