Baix (French pronunciation: [bɛks]; Occitan: Bais) is a commune in the Ardèche department in the Auvergne-Rhône-Alpes region of southern France.

Baix is located some 30 km (19 mi) south by southwest of Valence and 25 km (16 mi) northeast of Aubenas. Access to the commune is by the D86 road from Le Pouzin in the north which passes through the commune and the town and continues south to Cruas. The D22 branches off the D86 just inside the northern border of the commune and goes west to Chomérac. The commune is mostly forested but with farmland in the northwestern third of the commune.

The Rhône river forms the eastern border of the commune and the department as it flows south however there is no crossing point in the commune. The nearest crossing point is at Le Pouzin 5 km (3.1 mi) north. Numerous streams rise in the commune and flow east to the Rhone including La Payre, the Ravin de Roux, the Ravin de Saint-Pierre, the Ruisseau de Notre-Dame, the Ravin de Besset, the Ruisseau de Cournairet, the Ruisseau de Sainte-Euphémie, with the Ruisseau de Sichier forming the southern border of the commune.

The banks of the Rhone at Baix have been occupied since Roman times.

Many islands existed at the level of the plain of the Payre river which allowed for fords across the Rhone.

There was a Greco-Roman town between Le Pouzin and Baix which was at the junction between the Antoninus Pius Roman way on the right bank of the Rhône and the Via Agrippa on the left bank. It is possible that Hannibal, advancing out of Spain, crossed the Rhône at this place with his elephants in about 218 BC before crossing the Alps.

The name of this town was Batiana meaning "easy passage", a name probably given by a Phoenician colony to indicate the ease that of crossing the Rhone in this place (batos = 'easy' or 'feasible' with ana = 'crossing') thanks to number of islands in the river at this point.

Batiana had a ferry to cross the Rhône and a horse relay.