Technically, a mare is defined as a female horse over the age of three. A filly is a female horse three years or younger. Since the Kentucky Derby is a race for 3-year-olds only, no mare has ever won. However, three fillies have won the Kentucky Derby: Regret (1915); Genuine Risk (1980); and Winning Colors (1988).
Winning Colors, Genuine Risk, and Regret are the only fillies to win
Giacomo won the Kentucky Derby in 2005.
Ferdinard won the derby kentucky derby on 1986
A horse named Thunder Gulch won the Kentucky Derby in 1995.
Giacomo won the 2005 Kentucky Derby. He won with odds of 50-1.
Orb won the 2013 Kentucky Derby.
Nobody won the Kentucky Derby in 1400. It wasn't inaugurated until 1875.
California Chrome won the Kentucky Derby in 2014.
Middleground, ridden by jockey William Boland, won the 1950 Kentucky Derby.
The 14th Kentucky Derby was run in 1888 and won by MacBeth II.
The Kentucky Derby didn't begin until 1875.
The Kentucky Derby did not begin until 1875.