The Tricastini were a small Gallic tribe dwelling in the modern Tricastin region, near present-day Saint-Paul-Trois-Châteaux, during the Iron Age and the Roman period.
The Tricastini were probably one of the most ancient Celtic tribes of Gaul. They are first mentioned in Livy's legendary narration of Bellovesus' expedition from Gaul into Italy, then in his historical account of Hannibal's crossing of the Alps in 218 BC, when the Tricastini let the Carthaginian troops move across their land. After 121 BC, their territory was annexed to the province of Gallia Transalpina by the Roman Republic. By the 1st century AD, the Tricastini were part of the Cavarian confederation.