Silmaril (foaled March 31, 2001 in Maryland is an American thoroughbred mare racehorse. She is sired by stakes winner, Diamond, who in turn was sired by leading North American sire, Mr. Prospector. She was out of the mare, Kattebuck, whose sire was the 1985 United States Horse of the Year, Spend A Buck. Silmaril was also a very popular mare at Laurel Park Racecourse and throughout Maryland. She won two different races on Maryland Million Day, both the Maryland Million Oaks in 2004 as a three-year-old and the Maryland Million Distaff Handicap in 2006 as a five-year-old.