The Tricastin is an area around Saint-Paul-Trois-Châteaux in Provence, France. The name derives from the Gaulish tribe Tricastini, which was part of the confederation of the Cavares. The capital of the region, Saint-Paul was named Noviomagus before becoming Augusta Tricastinorum under Augustus's reign, and later Colonia Flavia Tricastinorum.
During Middle Ages, a confusion between Tricastini and Tria Castra (Three Castles) is responsible for the modern name of Trois Châteaux.
The wine Coteaux du Tricastin AOC is produced in the area.
Tricastin is also the name of a pressurized water reactor nuclear plant, Tricastin Nuclear Power Center.