Lexington (March 17, 1850 – July 1, 1875) was a United States Thoroughbred race horse who won six of his seven race starts. Perhaps his greatest fame, however, came as the most successful sire of the second half of the nineteenth century; he was the leading sire in North America 16 times, and broodmare sire of many notable racehorses.

Lexington was a bay horse with irregular white markings on his face and four white socks on his legs. 15.3 hands (63 inches, 160 cm) and was described as having good conformation though he had a distinctive convex profile, described as a "moose head." At stud, he developed a willful and somewhat vicious temperament. He was bred by Elisha Warfield at Warfield's stud farm, The Meadows, near Lexington, Kentucky. Lexington was sired by the Hall of Fame stallion, Boston.

Under the name of "Darley" Lexington easily won his first two races for Warfield and his partner, "Burbridge's Harry", a.k.a. Harry Lewis, a former slave turned well-known horse trainer. Lewis, being black, was not allowed to enter "Darley" in races in his own name, so the horse ran in Warfield's name and colors. Darley caught the eye of Richard Ten Broeck who asked Warfield to name his price. "Darley", the son of Boston, and Jarret, Lewis's son who was still enslaved, were sold in 1853 to Ten Broeck acting on behalf of a syndicate who would rename him Lexington. Affixed to Lexington's pedigree Warfield wrote: "The colt was bred by me, as was also his dam, which I now and will ever, own...E. Warfield."

A syndicate made up of Richard Ten Broeck, General Abe Buford, Captain Willa Viley, and Junius R. Ward, bought Lexington for $2,500 between heats (or during the running of his race), so tried claiming the purse money when he won. Failing that, he tried to deduct the purse money from the sale price. But Warfield held out. His new owners immediately sent Lexington to Natchez, Mississippi, to train under J. B. Pryor.

Lexington raced at age three and four and although he only competed seven times, many of his races were grueling four-mile events. Lexington won six of his seven races and finished second once. One of his wins was the Phoenix Hotel Handicap in 1853. On April 2, 1855, at the Metairie race course in New Orleans, he set a record running 4 miles (6.4 km) in 7 minutes, 19 3⁄4 seconds, running against time. Even with his complex and hard-fought rivalry with the horse Lecomte (also a son of Boston, both born just after Boston died), he was known as the best race horse of his day. His second match with Lecomte on April 14, 1855, was considered one of the greatest matches of the century. But Lexington had to be retired at the end of 1855 as a result of poor eyesight. His sire, Boston, had also gone blind. Conservation work in 2010 revealed that Lexington had had a massive facial infection that resulted in his going blind.

Lexington stood for a time at the Nantura Stock Farm of Uncle John Harper in Midway, Kentucky, along with the famous racer and sire, Glencoe. Sold to Robert A. Alexander for $15,000 in 1858, reportedly the then highest price ever paid for an American horse, Lexington was sent to Alexander's Woodburn Stud at Spring Station, Kentucky.

He stood for a price of $100 until 1861, when he first led the sire list, and it was increased to $200. He stood for a limited public fee of $500, the highest in the country and comparable to the leading English stallions, in 1865 and 1866 before being restricted to private stud duties only.

Called "The Blind Hero of Woodburn", Lexington became the leading sire in North America sixteen times, from 1861 through 1874, and then again in 1876 and 1878. Lexington was the sire of the undefeated Asteroid and Norfolk. Nine of the first fifteen Travers Stakes were won by one of his sons or daughters. Among his noted progeny are: