The Lake Çıldır is a large freshwater lake in the provinces of Ardahan and Kars in northeastern Anatolia, Türkiye.
It is located close to the borders with Georgia and Armenia. The Lake Çıldır is located at an elevation of approximately 1,959 m and is surrounded by a mountainous region. It has an area of 123 km2 and a maximum depth of about 42 m. Water from the lake is used for irrigation. The lake freezes over in the winter. The Lake Çıldır has an island near the shores of the village of Akçakale, where archaeological remains are preserved.