The Windsor Castle Stakes is a Listed flat horse race in Great Britain open to two-year-old horses. It is run over a distance of 5 furlongs (1,003 metres) at Ascot as part of the Royal Ascot meeting in June. It is currently run on the second day of the five-day meeting. From 2026 the Windsor Castle Stakes will be run over 6 furlongs and restricted to horses whose sire won over 7 furlongs or more as a two-year-old, or 8 furlongs or more as a three-year-old or older.