The Kentucky Derby (/ˈdɜːrbi/) is an American Grade I stakes race run at Churchill Downs in Louisville, Kentucky. The race is run by three-year-old Thoroughbreds at a distance of 1+1⁄4 miles (10 furlongs; 2,012 metres). Colts and geldings carry 126 pounds (57 kilograms) and fillies 121 pounds (55 kilograms).

Held annually on the first Saturday in May, the Derby is the first leg of the Triple Crown. It is preceded by the two-week-long Kentucky Derby Festival. The race is known as "The Run for the Roses", as the winning horse is draped in a blanket of roses. Lasting approximately two minutes, the Derby has been alternately called "The Most Exciting Two Minutes in Sports", "The Fastest Two Minutes in Sports", or "The Greatest Two Minutes in Sports", coined by Churchill Downs president Matt Winn. At least two of these descriptions are thought to be derived from the words of sportswriter Grantland Rice, when in 1935 he said "Those two minutes and a second or so of derby running carry more emotional thrills, per second, than anything sport can show."

The race was first run in 1875. Unlike the other, older races of the Triple Crown—the Preakness Stakes and the Belmont Stakes—along with the Travers Stakes (the oldest comparable stakes race in the US), the Kentucky Derby and its sibling race, the Kentucky Oaks, have been run every year since inception. They were twice rescheduled within the same year, the first time due to World War II in 1945, and the second time due to the COVID-19 pandemic in 2020. The Derby and the Oaks are the oldest major sporting events in the US held annually since their beginning. Among thoroughbred stakes races, they are the oldest that have been held annually on the same track every year.

The Derby is the most-watched and most-attended horse race in the United States. The 151st running took place on Saturday, May 3, 2025.

In 1872, Col. Meriwether Lewis Clark Jr., grandson of William Clark of the Lewis and Clark Expedition, traveled to England, visiting Epsom in Surrey where The Derby had been running annually since 1780. From there, Clark went on to Paris where a group of racing enthusiasts had formed the French Jockey Club in 1863. They had organized the Grand Prix de Paris at Longchamp, which at the time was the greatest race in France. Returning home to Kentucky, Clark organized the Louisville Jockey Club and Driving Park Association to raise money for building quality racing facilities just outside the city. First known as the Louisville Jockey Club grounds, seven years later the track was commonly referred to as Churchill Downs, named for John and Henry Churchill, who provided the land for the racetrack. The naming went official in 1937.

The Kentucky Derby was first run at 1+1⁄2 miles (12 furlongs; 2.4 km) the same distance as the Epsom Derby, before changing lengths in 1896 to its current 1+1⁄4 miles (10 furlongs; 2 km). On May 17, 1875, in front of an estimated crowd of 10,000 people, a field of 15 three-year-old horses contested the first Derby. Under jockey Oliver Lewis, a colt named Aristides, who was trained by future Hall of Famer Ansel Williamson, won the inaugural Derby. Later that year, Lewis rode Aristides to a second-place finish in the Belmont Stakes.

In these early decades, Black jockeys were very influential at the Derby. Horses, including race horses, had been cared for, trained and exercised by Blacks in the ante-bellum slave-holding states and this expertise laid the groundwork for future racing standards. Jockeying was seen as activity unsuitable for Whites during that era and in the decades after the Civil War when it was becoming lucrative. Black jockeys dominated the Derby in all the years before 1894, except for one. In 1886 the track, which had been successful, ran into financial difficulties when a protracted, gambling-related horseman boycott removed it from the upper echelons of racing until just after the turn of the 20th century. In 1894 the New Louisville Jockey Club was incorporated with new capital and improved facilities. The rise of on-track betting and increasing audience sizes brought larger purse sizes, and this began to attract White jockeys to the profession. White jockeys on tracks everywhere began to use violence to attack and intimidate Black jockeys and the horses they rode. This caused horse owners to stop hiring Black jockeys. Though they were consistent Derby winners, Black jockeys began to disappear from the Derby after 1894. Jimmy Winkfield was the last Black jockey to win the derby and Black jockeys were gone by 1911. But they had instituted innovations now universal in the sport. Wille Simms won the Derby in 1896 and 1898 on the shortened stirrups he evolved from those used by Black jockeys before him. After his racing career, Oliver Lewis began collecting and analyzing racing data, developing a system very much like the ones used today.

Initially a successful venue, the track ran into financial difficulties due to a protracted, gambling-related horseman boycott removing it from the upper echelons of racing that would last until just after the turn of the 20th century. In 1894 the New Louisville Jockey Club was incorporated with the new capital and improved facilities. Despite this, the business floundered until 1902, when a syndicate led by Col. Matt Winn of Louisville acquired the facility. Under Winn, Churchill Downs prospered, and the Kentucky Derby then became the preeminent stakes race for three-year-old thoroughbred horses in North America.