Castejón de las Armas is a municipality in the province of Zaragoza, in the autonomous community of Aragon, Spain. It is a small settlement in the Jalón river valley area of the province.
The River Piedra joins the Jalón at Castejón de las Armas, a confluence that defines the village's immediate geography. According to the 2004 census (INE), the municipality had a population of 99 inhabitants, reflecting the sparse population typical of much of rural Aragon.