Ytre Storevatnet is a lake in the municipality of Bykle in Aust-Agder county, Norway. It is the northernmost part of the Svartevatnet reservoir that empties into the Sira River system. The lake is located just south of the lake Blåsjø and southwest of Botsvatn. The village area of Bykle is about 25 kilometres (16 mi) northeast of the lake.