One Master (foaled 1 April 2014) is a British Thoroughbred racehorse. She did not race until she was a three-year-old when she won two of her three races including the Listed October Stakes. In the following year she was beaten in her first three starts before taking the Group 3 Fairy Bridge Stakes in Ireland and the Group 1 Prix de la Forêt in France. As a five-year-old in 2019 she repeated her victory in the Prix de la Forêt as well as being placed in the Queen Anne Stakes, Falmouth Stakes and British Champions Sprint Stakes. In 2020 she won the Oak Tree Stakes and took the Prix de la Forêt for a record third time.