The Prix de Royallieu is a Group 1 flat horse race in France open to thoroughbred fillies and mares aged three years or older.
It is run at Longchamp over a distance of 2,800 metres (about 1 mile and 6 furlongs), and it is scheduled to take place each year in late September or early October.
The event is named after Royallieu, an area where the stables of Frédéric de Lagrange were located in the late 19th century.
The original version was open to horses of either gender aged three or older.
The Prix de Royallieu was opened to older fillies and mares in 1965.