Astarac (French pronunciation: [astaʁak]) is a region in Gascony, a county in the Middle Ages. Astarac was formed as a county out of the partition of the Duchy of Gascony: following the death of García II Sánchez of Gascony, the duchy was partitioned between his sons, with Arnold I, the youngest son, receiving Astarac.
Astarac borders Armagnac to the northwest, the Rivière-Basse and Bigorre to the west, the Magnoac to the southeast, and Comminges to the east. Its principal cities are Mirande, Masseube, Miélan, Tournay, Pavie, Idrac-Respaillès, Castelnau-Barbarens, Berdoues, Ponsampère, Mont-d'Astarac, Miramont-d'Astarac, Laas d'Astarac, and Fontrailles.