Syndle (historic: "Søndlevatn") is a lake in the municipality of Grimstad in Agder county, Norway. It is located in the Landvik area, about 5 kilometres (3.1 mi) northwest of the center of the town of Grimstad. The 6-square-kilometre (2.3 sq mi) lake Syndle flows into a small river on the northeast part of the lake which connects it to the neighboring lake Rore which eventually flows into the river Nidelva.