Arignac is located 2 km north of Tarascon-sur-Ariège and some 11 km south of Foix. Access to the commune is by road D88 from Tarascon-sur-Ariège in the south passing through the village and continuing north-east to join National Highway N20 at Exit 14. The N20 passes through the south-east of the commune but the nearest exit is Exit 14 just east of the commune. The town covers about 10% of the commune with the rest mostly forest and hill country with a few farms in the south.[3]
The Ariège river forms the south-eastern border of the commune and the Saurat flows south through the commune and the town to join the Ariège.[3]