Sástago is a municipality in the province of Zaragoza, in the autonomous community of Aragon, Spain. It is located in the Ebro River valley in northeastern Spain, within the comarca of Ribera Baja del Ebro.
According to the 2004 census (INE), the municipality had a population of 1,307 inhabitants. The town is situated near the Ebro, the longest river in Spain, which flows through Zaragoza province and shapes the surrounding agricultural landscape.