Astarac (French pronunciation: [astaʁak]) (or Estarac) is a region in modern-day departments of Gers and Hautes-Pyrénées.

Bordering on the Lannemezan plateau, it is a very hilly region with clay soil, crossed by several rivers including the Baïse, Arrats and Gers, which have led to the formation of artificial lakes such as the Lac de l'Astarac.

Astarac borders Armagnac to the northwest, the Rivière-Basse and Bigorre to the west, the Magnoac [fr] 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.

Linguist Joan Coromines likens this name to the biscayan word: azterren, meaning 'root' or 'foundation'.