Lake Küçükçekmece (Turkish: Küçükçekmece Gölü) is a lagoon located between the Küçükçekmece, Esenyurt and Avcılar districts of the European portion of Istanbul Province, northwestern Turkey. The lake is neighbored in the south by state road D.100 and in the north by the O-3 motorway (European route E80).
Situated 15 km west of Istanbuls city center, the lake was formed in shallow water when a sandbank caused its separation from the Sea of Marmara. A narrow channel in the east interrupts this sandbank, and serves as an outlet emptying excessive water in the lake into the Sea of Marmara. However, in situations where the sea is rough or the lakes water level gets too low due to drought, sea water may penetrate into the lake, causing the lake water to become brackish. The lake is fed from the north by the Nakkaş, Sazlıdere and Eşkinoz streams. The lake has a length of 10 km north-south by a maximum width of 6 km. The lakes surface area is 16 km2, and its maximum depth is 20 m.
