[2] Bred by Robert Ryan, Ballymorris Stud, Royal Heroine was out of the mare My Sierra Leone, a daughter of the 1963 Epsom Derby winner, Relko.
Racing at age two, Royal Heroine won two of four starts including a victory in the Princess Margaret Stakes at Ascot Racecourse.
[3] In winning the inaugural running of the Breeders' Cup Mile at Hollywood Park Racetrack, Royal Heroine defeated a field of nine male horses.
Although bred to notable sires such as Sadler's Wells and American Triple Crown winner, Affirmed, none achieved success in racing.
However, her daughter Castilian Queen (Diesis) did produce the French Grade 1 Prix de l'Abbaye winner Carmine Lake (Royal Academy).