The Prix Niel is a Group 2 flat horse race in France open to three-year-old thoroughbred colts and fillies.
It is run at Longchamp over a distance of 2,400 metres (about 1½ miles), and it is scheduled to take place each year in September.
It was open to horses aged three or older, and for a period its distance was 3,100 metres.
The Prix de Chantilly was restricted to three-year-olds when a separate event was introduced for older horses in 1955.
The event was renamed in memory of Gaston Niel (1880–1970), a long-serving member of the Société d'Encouragement, in 1972.