James E. Day (born July 7, 1946, in Thornhill, Ontario) was a Canadian Olympic equestrian show jumping champion and Thoroughbred horse trainer.
Day first joined the Canadian Equestrian Team in 1964, and in 1966 tied the record high jump of 7 feet 1 inch at the National Horse Show in New York. Day took gold in individual jumping at the 1967 Pan American Games. Day was named Canada's Horseman of the Year three years running in 1966 through 1968. In the 1972 Olympics in Munich he finished 4th individually, and a team 6th. In the 1976 Summer Olympics he competed in both the show jumping and three-day eventing competitions, coming in 15th individually and 5th team in the show jumping, and not finishing the three-day eventing competition, although the Canadian team came in 6th.