What is Filly? Filly Explained in 2 minutes
Jesse M. Cox Last Verified
26/06/2026
A filly is a young female horse, usually under four years of age – although in the UK and the USA the cut off point for referring to horses as fillies is five years old. When fillies pass their age group they are called mares – whereas the naming of male horses goes from colt to stallion.
How is Filly used in Sports Betting?
Although fillies and colts regularly race together there are a number of big horse races that are strictly reserved for fillies of three years of age.
Flat races are the most common format in the UK and there are a group of very popular races that are reserved for young horses – fillies and colts – of three years of age. Collectively these five races are called the Classics, but they are made up of two distinct sub-groups – the Triple Crown and the Fillies’ Triple Crown. The 1,000 Guineas Stakes at Newmarket, the Epsom Oaks and the St Leger Stakes, which is run at Doncaster, are the three filly only classics.
As the Classics are so popular with the punters, bookmakers will offer ante post betting throughout the year. This means that the possibility of getting some excellent value odds is possible for those in the know.
Did You Know...
Oh So Sharp is one of the most famous British-trained fillies – due mostly to winning the Fillies’ Triple Crown in 1985. Her racing career only lasted from August 1984 until September 1985, in which time she won seven out of nine races. Oh So Sharp was favourite for all her races and never raced at odds of more than 2/1.
