Arkle was an Irish Thoroughbred racehorse. A bay gelding by Archive out of Bright Cherry, he was the grandson of the unbeaten flat racehorse and prepotent sire Nearco. Arkle was bred by Mary Baker of Malahow House, near Naul, County Dublin, Ireland, and was born at Ballymacoll Stud, County Meath. He was owned by Anne Grosvenor, Duchess of Westminster, who named him after the mountain Arkle in Sutherland, Scotland, that bordered her Sutherland estate. Trained by Tom Dreaper at Greenogue, Kilsallaghan, in County Dublin, he was ridden during his steeplechasing career by Pat Taaffe.

Nearco was an Italian-bred Thoroughbred racehorse described by Thoroughbred Heritage as "one of the greatest racehorses of the Twentieth Century" and "one of the most important sires of the century." He was unbeaten, winning 14 races at distances from 1000m to 3000m, including the Derby Italiano and Grand Prix de Paris. He was then sold for a record amount to Martin H. Benson and stood stud in England, where he became the patriarch of several of the most dominant sire lines in Thoroughbred history.