Partner (also known as Croft's Partner or Old Partner) was a British Thoroughbred racehorse and sire. He won six of his seven races before being retired to stud where he was the Leading sire in Great Britain and Ireland four times, and continued the Byerley Turk sire-line.
Partner's breeder sold him to Mr. Cotton of Sussex, who in turn sold him to Lord Halifax. Lord Halifax raced the colt with great success over four mile courses. He was unbeaten in 1723 and 1724, taking the following year off to come back to the track in 1726, beating Sloven in a match race. His only loss was in a race in 1728 to Smiling Ball, after which he was sold to John Croft to begin his breeding career.
His most important son was Tartar, who went on to sire the very influential Herod. He also sired Cato, Golden Ball, Sedbury, Morton's Traveller, (b c 1746 - exported to United States and a good sire there) and Traveller (1735), as well as the dam of Matchem, before his death at 29.