Lake Erçek (Turkish: Erçek Gölü, Armenian: Արճակ լիճ) is an endorheic salt lake in Van Province in eastern Turkey, about 30 kilometres east of Lake Van. The lake sits at an elevation of about 1,803 metres, and has an area of 106.2 square kilometres and a mean depth of 18.45 metres. The northern and western shores are steep and rocky, whereas the southern and eastern shores slope gently with mudflats and coastal plains.
The lakes main inflow is from the Memedik Çayı (also known as the Büyükçaylak Deresi), which enters via a broad fan at the west of the lake. The Karasu river, which rises along the Iranian border, passes within 1 kilometre of the northwest shore of the lake and is separated only by a low ridge, but it does not enter the lake and continues west to enter Lake Van northwest of the city of Van.
