Lake Sapanca is a fresh water lake in Türkiye, between the Gulf of İzmit and the Adapazarı Meadow. The lake has a catchment area of 251 km², surface area is 45 km², a length 16 km east–west / 5 km north–south, and a maximum depth of 52 m. Lake Sapanca, Türkiye

Sapanca Lake is located on a tectonic hole, which is situated between Izmit Bay and Adapazari Meadow and runs parallel to Iznik Lake.

The catchment area of Lake Sapanca - about 251 km2 [km²] - is surrounded by mountains in the south and small hills in the north. 

The region around Sapanca is an important destination for day trips and weekend vacations.