Attalus I (), surnamed Soter (, "Savior"; 269–197 BC) ruled Pergamon, an Ionian Greek polis (what is now Bergama, Turkey), first as dynast, later as king, from 241 BC to 197 BC. He was the second cousin and the adoptive son of Eumenes I, whom he succeeded, and was the first of the Attalid dynasty to assume the title of king in 238 BC. He was the son of Attalus and his wife Antiochis.