The St. Simon Stakes is a Group 3 flat horse race in Great Britain open to thoroughbreds aged three years or older.
It is run at Newbury over a distance of 1 mile and 4 furlongs (2,414 metres), and it is scheduled to take place each year in October.
The event is named after St. Simon, an undefeated racehorse in the 1880s and subsequently a successful sire.
The present system of race grading was introduced in 1971, and the St. Simon Stakes was initially given Group 2 status.
The St. Simon Stakes is part of Newbury's last flat racing fixture of the year.