Diomed (1777–1808) was an English Thoroughbred race horse who won the inaugural running of the Epsom Derby in 1780.

Sold and imported to Virginia, he was subsequently a successful sire in the United States after the American Revolutionary War.

A bright chestnut standing 15 hands (60 inches, 152 cm),[1] he was named after the Ancient Greek hero Diomedes.

Richard Vernon and owned by Sir Charles Bunbury, 6th Baronet,[1] then trained by him at Hilton Hall.

[2] During these early bright years of Diomed's life, he was considered by many to be the best colt seen in the Britain since Eclipse in 1769 and 1770.

Over the next decade or so, interest in Diomed as a sire declined, as several of his sons became known for having temperament problems, stubbornness, and too much excitability.

Aside from importing bloodstock into the United States, Hoomes also maintained his own racing stable and stud service in which his good friend, the leading national horseman of the time, John Tayloe III, was a partner.

Diomed's offspring competed with many of the greatest horses in American turf history: Haynie's Maria (b.

1808), about whom Andrew Jackson said, "...Haynie's Maria can beat anything in God's whole creation";[6] Ball's Florizel (b.

Sir Archy had a huge influence on Thoroughbred history in the United States, siring the line which led to Timoleon, Boston, and Lexington.

Furthermore, Diomed's influence has been felt through his sons regarding the development of the breeds American Quarter Horse (Sir Archy) and Standardbred (Duroc).