Jack Spigot (4 May 1818 –June 1843) was a British Thoroughbred racehorse that won the 1821 St. Leger Stakes and was a sire in the early 19th century.

A dapple grey foster mare similar in colouring to his own dam was procured from one of Powlett's tenants, Jack Faucet, to raise the foal.

Faucet objected to the choice on the grounds that the horse was a good candidate for winning that year's St. Leger.

After his St. Leger win, Jack Spigot developed an intense dislike of the jockey and would react violently if Scott attempted to approach the horse or even spoke in his presence.

In his only start as a two-year-old, Jack Spigot, ridden by Bill Scott, won a 320 guinea sweepstakes race at Doncaster Racecourse beating Mr. Riddell's colt Colwell.

[13] Jack Spigot did not run until the autumn Doncaster meeting and on 17 September started in the St. Leger Stakes against 12 other horses including the 1821 Derby winner Gustavus.

[14] Two days later he won the Foal Stakes over a distance of one and a half miles beating his only competitor, the filly My Lady, in a "very excellent race.

Jack Spigot only ran once more, on 14 April 1823 he was unplaced in the Craven Stakes won by the Duke of Rutland's colt Scarborough.

[16] Thomas Orde-Powlett retired from racing in September 1823 and put his horses up for sale at the Doncaster meeting.