Lake Çıldır (Türkçe. Çıldır; Armenian: Հիւսիսեան (Latin transliteration: Hiusisean); Georgian: ჩრდილი (Latin transliteration: Chrdili meaning "Shadow" in Georgian); русский. Чилдыр) is a large freshwater lake in the Ardahan Province, northeastern part of Turkey. It is located at , close to the borders with Georgia and Armenia. Lake Çıldır is located in the elevation of about 1,900 m and surrounded by mountainous region. It has an area of 123.00 km² and maximum depth of about 42 m. Water from the lake is used to irrigation.
