The Irish Derby is a prestigious Group 1 flat race held annually at Curragh Racecourse in County Kildare usually in late June or early July. Open to three-year-old thoroughbreds, it covers 1 mile 4 furlongs (2,414 metres). Established in 1866, the race is a highlight of the Irish racing calendar attracting top horses, jockeys and trainers. It is regarded as a key event for assessing future success in major races.