Castejón de Valdejasa is a municipality in the province of Zaragoza, in the autonomous community of Aragon, Spain. It is located in the comarca of Cinco Villas, in the northern part of the province, an area of dry farmland and low hills on the edge of the Ebro basin.
The municipality is small and sparsely populated. According to the 2004 census (INE), it had a population of 315 inhabitants. Like many rural settlements in inland Aragon, it has experienced a long-term decline in population as residents have moved to larger cities such as Zaragoza.
Its economy has traditionally been based on agriculture, particularly dryland cereal crops, along with livestock, reflecting the semi-arid conditions of the surrounding region. The village retains a compact historic core typical of Aragonese rural settlements, with the church and town hall among its main buildings.