Vaison-la-Romaine (Latin: Vasio Vocontiorum) is a commune in the Vaucluse department in the Provence-Alpes-Côte d'Azur region in southeastern France.
The historic section is in two parts, the Colline du Château on a height on one side of the Ouvèze, the "upper city" and on the opposite bank, the "lower city" centered on the Colline de la Villasse.
At Vasio Pompeius Trogus, the Augustan historian, was born.
The barbarian invasions were presaged by a pillaging and burning in 276, from which Roman Vasio recovered, but in the fifth century the benches of the theatre began to be reused as Christian tombstones. Vaison belonged the Burgundians, was taken by the Ostrogoths in 527, then by Clotaire I, King of the Franks in 545, and became part of Provence
The disputes which broke out in the twelfth century between the counts of Provence, who had refortified the ancient "upper town" and the bishops, each of whom were in possession of half the town, were injurious to its prosperity; they were ended by a treaty negotiated in 1251 by the future pope Clement IV, a native of Saint-Gilles-du-Gard.