Lake Urmia is an endorheic salt lake in Iran. The lake is located between the provinces of East Azerbaijan and West Azerbaijan in Iran, and west of the southern portion of the Caspian Sea. At its greatest extent, it was the largest lake in the Middle East and the sixth-largest saltwater lake on Earth, with a surface area of approximately 5,200 km² (2,000 sq mi), a length of 140 km (87 mi), a width of 55 km (34 mi), and a maximum depth of 16 m (52 ft).

By late 2017, the lake had shrunk to 10% of its former size (and 1/60 of water volume in 1998) due to persistent general drought in Iran, but also the damming of the local rivers that flow into it, and the pumping of groundwater from the surrounding area. This dry spell was broken in 2019 and the lake is now filling up once again, due to both increased rain and water diversion from the Zab River by the Urmia Lake Research Programme.

Lake Urmia, along with its approximately 102 (former) islands, is protected as a national park by the Iranian Department of Environment.