Longerakvatnet or Longeraksvatnet is a lake in the municipality of Bygland in Agder county, Norway. It has a small dam on the southwest side to regulate the water level for hydro-electric power generation at a plant located down the hill. The lake discharges into the Longeraksåni river which flows into the Byglandsfjorden near the village of Longerak. The 3.4-square-kilometre (1.3 sq mi) lake is located about 6 kilometres (3.7 mi) southeast of the village of Lauvdal and about 10 kilometres (6.2 mi) northeast of the village of Byglandsfjord.

• List of lakes in Aust-Agder
• List of lakes in Norway