Aouste is located some 35 km south-east ofHirson and 40 km west by north-west ofCharleville-Mézières. Access is by the D36 road fromLa Férée in the south passing through the village then continuing east toPrez. The D27 road also comes fromRumigny in the west passing through the commune south of the village and continuing toMarlemont in the south-east. A railway from Hirson to Charleville-Mezieres passes through the commune with a station atLiart just outside the commune to the south-east. Apart from the village the commune is mostly farmland with a few patches of forest.
TheAube river passes through the commune from the east and flows through the village before continuing west to join theTon atHannappes. TheRuisseau de Laval d'Estrebay flows from the north forming part of the northern border to join theAube on the western border. There is also theRuisseau du Moulin Veron which flows from the south joining the Aube near the village. TheRuisseau de Gandlu flows from the south-east joining theAube in the village.[3]