A filly is a young female horse , usually one that is under 4 years old ; in horse racing, some use the term for females under 5. It’s the female version of a colt , and once she’s older, she’s usually called a mare.

Quick Scoop

  • Filly = young female horse.
  • Colt = young male horse.
  • Mare = adult female horse.
  • In some racing contexts, “filly” can extend to age 5.

If you want, I can also give you a super-short horse terms cheat sheet like foal, colt, filly, gelding, stallion, mare.