Castejón de Alarba is a municipality in the province of Zaragoza, in the autonomous community of Aragon, Spain. It is a small rural settlement in the comarca of Comunidad de Calatayud, in the northeastern part of the country.
The municipality is sparsely populated. According to the 2004 census (INE), Castejón de Alarba had a population of 98 inhabitants, reflecting the low population density typical of many villages in this part of Aragon.
Its administrative status as a municipality places it among the many small local entities that make up the province of Zaragoza. The town is situated in the Iberian Peninsula's interior, within the Ebro basin region that defines much of Aragon's geography.