Lake Urmia is an endorheic salt lake in Iran. The lake is 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). The lake has shrunk to 10% of its former size due to damming of the rivers that flow into it, and the pumping of groundwater from the surrounding area.
Lake Urmia, along with its once approximately 102 islands, is protected as a national park by the Iranian Department of Environment.
The lake was the center of the Mannaean Kingdom. A potential Mannaean settlement, represented by the ruin mound of Hasanlu, was on the south side of the lake. Mannae was overrun by the Matiani or Matieni, an Iranian people variously identified as Scythian, Saka, Sarmatian, or Cimmerian. It is not clear whether the lake took its name from the people or the people from the lake, but the country came to be called Matiene or Matiane, and gave the lake its Latin name.