Antinoüs, was a chestnut colt bred and owned by Augustus Fitzroy, 3rd Duke of Grafton, and named after one of the much-admired antique marble sculptures representing the youth associated with the Emperor Hadrian, which the young Duke could have seen in Rome during his prolonged Grand Tour, 1753-62. Foaled in 1758 by Blank out of a mare by Partner, Antinoüs had a very good pedigree as his dam was a full sister to the Widdrington Mare. He ran very successfully from 1762 to 1767, winning eight out of twelve races. He also received two forfeits and in total won the Duke of Grafton nearly £5,000 (1,200 guineas of which was won in a single important sweepstake at Newmarket in early April 1763). Three of his four defeats were by very well known horses: Herod beat him in both their matches (in the first Antinoüs started as 6-4 on favourite against the great champion), and he was also beaten by Otto and Exeter. In 1768 he retired to a farm called Little Fakenham on (or near) the Grafton estate at Euston near Thetford. He initially stood at 5 guineas but the fee was raised to 10 guineas in 1775 in response to the successes of Euston who, together with Leapfrog, were his best winners.
Throughout his stud career, Antinoüs was managed by his former jockey, William Pilkington, who is shown riding the horse in another picture by Stubbs, 40 x 50 in., commissioned by the 3rd Duke of Grafton, and exhibited in 1764 (British private collection; see J. Egerton, George Stubbs, Painter, New Haven and London, 2007, no. 43, p. 184, illustrated p. 185). An old label on the reverse of the present picture errs slightly in suggesting the subject was 'a favourite horse of Rd. Stonehewer'. A portrait of Stonehewer was in the Grafton sale in these Rooms, 27 June 1921, lot 101 (see D. Mannings, Sir Joshua Reynolds, A complete catalogue of his paintings, New Haven and London, 2000, p. 436, no. 1716, fig. 1158).